HVAC compressor / condenser diagnostic questions & answers or FAQs:

This air conditioning repair article provides diagnostic questions & answers for the outdoor compressor / condenser unit used on air conditioners & heat pumps. These questions and answers help diagnose an compressor motor that is not working, compressor noises, condensing coil performance, or for heat pumps, outdoor coil icing.

Diagnostic Questions & Answers for the Outdoor Compressor/Condenser Unit

These questions and answers about troubleshooting and fixing air conditioner or heat pump compressor/condenser units were posted originally at COMPRESSOR / CONDENSER DIAGNOSTICS - be sure to check out the diagnostic suggestions on that page.

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Question: AC unit not cooling, very hot high pressure refrigerant line

our AC unit is not cooling, the high pressre line is VERY hot and the low pressure line is not much colder than room temp. last year we put in a new evap coil.. any ideas - Rusty 7/31/11

Reply:

Rusty, you need an expert on site to diagnose the problem. There are several problems that can give excessive pressure/temperature on the compressor outlet side of the system (the high side).

Sounds like a blockage, maybe clogged dryer or bad refrigerant metering device, sometimes a clogged condensing coil.

Question: Outside AC turns on but no cool air is delivered inside. What's the cause?

our AC outside turns on but it does not blow any air inside what can be the cause of this? - Veronica 8/2/11

Reply:

Veronica if the outside compressor/condenser is working but the inside air handler/fan unit is not, take a look at the diagnostic article BLOWER FAN OPERATION & TESTING (links at the ARTICLE INDEX the bottom of this article )

It could be as simple as a fan drive belt that has broken in an air handler, or a dirty air filter.

Question: can't get up to working refrigerant pressure level

The discharge line from my condenser is giving only 100 PSI, even after adding R-22 to the low side. Is my compressor defective? - Carlos 8/11/11

Reply:

Carlos, could be a bad compressor but it could also be a bad thermostatic expansion valve that is not closing.

Question: new AC unit, has trouble starting up / compressor fan won't start

my air conditioner is new. its been hardly four month since i purchased it. most of the times it tries to start 2 to 3 time and then get started and some times unable to start. i dont have stablizer in my house for ac. when it runs it runs smooth and when it trips same case occur like starting can you please comment the possible casuse - Waquar Zaidi

(July 20, 2015) lewis said:
Took the top off the unit. The fans spins by hand but wont turn on and run. Could it be the condesor

Reply:

Lewis: if the compressor motor runs but the compressor/condenser fan won't run see FAN, COMPRESSOR / CONDENSER DIAGNOSTIC FAQs and check for a bad fan start run capacitor or a bad fan relay.

Wagar I'm surprised to read that a new A/C system compressor is not starting, but I suppose it could be a bad start capacitor or another bad control such as the Thermostatic Expansion valve.

There are perhaps a few mistakes that could happen during installation that could destroy even a new A/C compressor such as dirt in the system or an improper refrigerant charge or a bad TEV that slugged the comprssor with liquid.

I'm unclear about the second and third sentences of your question.

Reader followup:

2nd and 3rd sentence i would like to elaborate: when compressor starts its working fine i mean it cools the room i use to run it on 26 degree centigrade and when thermostat trips and after 10 to 12 mints when compressor again tries to start same problem comes. and some time with out problem, compressor starts in first attempt.

is this a compressor problem what will happen if i continue to run my ac in this situation. thanks in advance

Reply:

AHA Wagar,

I can't pretend we can really diagnose by e-text Q&A, but if I understand more clearly, you are saying that the A/C compressor starts and runs OK the first time, but after the thermostat is satisfied and stops the cooling system compressor/condenser, when the temperature in the building rises and the TT calls for cooling a second time, the compressor is having trouble starting.

A simplistic view would be to treat it as a "hard starting compressor" and install a hard start capacitor kit. But since the compressor starts OK cold, it might be a different trouble.

If the compressor is trying to re-start against high head pressure that is more difficult than starting "cold" when the refrigerant pressures are the same on both high side and low side of the system.

So I'd look into what would cause head pressure to remain high after the compressor stops running. In many HVACR systems, as soon as the compressor stops running the pressures begin to equalize on the two sides of the system.

See COMPRESSOR / CONDENSER DIAGNOSTICS

• HVAC COMPRESSOR WON'T START

For more diagnostic help see the article REFRIGERANT PRESSURE READINGS & CHARTS and REFRIGERANT PRESSURE CONTROLS & SWITCHES

Reader followup:

it even having same problem in first time start and now these days after its thermostat satisfies its not restarting after several attempts.

what i am concerned is: is it a compressor problem? or capacitor. or possibly some thing else when ac start it works fine i am as far as cooling is concerned there is no problem with cooling once it get success in starting. - Waqar

Reply:

Waqar why don't you try a hard-start capacitor kit

Reader followup:

Thanks Mod, will definitely try actually i am away from my home town will reach in 15 days. i would like to thanks you for your support you provided and will let u know the results.

Question: start/run capacitor changed, but now nothing works

I changed equivalent capacitor after that it was ok to startup.
Now i need to turn on back, but it di dnot startup. i need to turn off siwtch then tunr on back switch in order to startup again.
Why is it?
Thanks, CHang - 8/26/11

Reply:

I'm not sure, Chang. Double check your capacitor to see that it's matched in rating to the original and that you wired it correctly.

Question: outside fan won't run, A/C is making a hissing noise

fan on outside unit does't run the ac runs but does not cool makes hissing noise - Nancy 9/7/11

Reply:

Nancy, See NOISES, COMPRESSOR CONDENSER (article link at the ARTICLE INDEX the bottom of this article ) to diagnose various A/C system sounds,

Watch out: If you hear a loud high pitched noise at the compressor, turn off electrical power to the unit immediately.

Other more quiet hissing noises from the air conditioner compressor motor may (if the motor is a reciprocating compressor) be due to leaky internal valves.

The compressor motor makes a hissing sound all during the time the compressor is running; when the motor stops the hissing dies down fairly quickly as the high side and low side pressures equalize. In this case the condition may not be dangerous, just an inefficient system that is costly to operate.

Question: outside air conditioner compressor made a loud noise, then smoked, now it seems to be working

(Jan 4, 2015) linda cape said:
my compressor made a loud noice,then puff of smoke came out.I turned it off,when I turned it on again it worked and is heating.any known reason for this?

Reply:

Linda I dont know what happens but it doesn't sound good. If it was really smoke -as in something burning, I'd leave the unit off and ask for a service call.

Possibly it was not true smoke but a refrigerant leak which might, depending on leak rate and weather, might appear as white "smoke'. - Also a need for a service call.

it's also possible your system is running but on backup heat.

DO let us us know what your heating service tech finds as it will assist other readers. And do not avoid a service call since if there was a leak or burn-up the system may be unsafe.

Question: air conditioner compressor shuts down after 30 minutes or less - short cycling HVAC compressor / condenser unit

My compressor shuts down after only 30 minutes or less, it starts fine, but cooling seems to be a bit less then before, and none at all once it shuts down. I open the breaker for a short time and it will run again, then shut down. - Darrell M 9/8/11

(Aug 6, 2014) mike said:
my a/c,compressor stars up and runs for 5 minutes before stopping,it's cooling for those 5 minutes it's running.I did replace the 50+5 cap. but it did not make a difference.

Reply:

Darrell, it sounds as if a compressor motor may be overheating; when you leave power off for a time the motor cools down enough that its own internal thermal reset in fact resets itself.

I'd call a service technician for more thorough diagnosis.

By no cooling, if you mean there is airflow but the air is not cool, that's consistent with above.

Mike: Check for an overheating motor or a control board or relay snafu

See HVAC COMPRESSOR SHORT CYCLING ON & OFF

Question: air conditioner or heat pump compressor / condenser won't shut off

(Apr 29, 2015) Raymond said:
My air conditioner compressor keeps running even when I put the thermostat on heat. I just had a new furnace installed this winter and there are two wires coming from the compressor one is red and one is white.

I connected the whit to the letter "C" on the furnace and the red to the red wire.

I tried to connect the white wire to the yellow, green and white wires but the compressor would not energize. when I connected the white wire to the "C" contact in the furnace the compressor came on runs fine and puts out cold air but will not shut down when I switch to heat?

Reply:

First check that the thermostat is set above room temperature or is in the OFF position.

Then see COMPRESSOR / CONDENSER DIAGNOSTICS where we include HVAC COMPRESSOR WON'T STOP

Question: My A/C compressor just won't stop running

I recently noticed my AC condenser unit still running when the system inside shutoff by itself. and also, does the condenser unit have to be leveled. I notice the slap which holding the unit is slopping. Any suggestions? Thank you. - Rick 8/16/11

Reply:

A/C compressor/condenser won't stop running:

Rick usually when an A/C condenser unit won't stop running even though the inside equipment has shut off by itself my thinking divides into two investigations:

- is there a problem with the INDOOR unit such as a blower fan that won't start, an access door switch open, a condensate drain switch turning off the blower unit - these can leave the system calling for heat and the compressor running (though that's not good for the compressor)

- is there a problem with the outdoor equipment such as a bad control relay or control board

See COMPRESSOR / CONDENSER DIAGNOSTICS

Question: the Haier AC unit is forming frost or ice on the coil

my question is i have turned off my 1 ton haier ac its inner unit is shut off but not outer unit due to which it it creates ice in inner unit can you let me know what is the issue. Thanks !! - Asim Niaz 9/15/11

Reply:

Asim, if the indoor blower unit is not running and the outdoor compressor is running the lack of air movement across the evaporator coil will lead to frost and ice formation on the coil. Under COOLING COIL or EVAPORATOR COIL you'll find diagnosis of ice or frost blocked cooling coils.

Question: I filled up my air conditioner with gas but now what?

So what is the solution of this problem as i have already filled gas recently. Thanks !! - Anon 9/16/11

Reply:

You need a service call from an experienced diagnostician. We don't have enough information about your case to specify a fix.

Or take a look at LOST COOLING CAPACITY for more diagnostic guides
(article link is at the ARTICLE INDEX the bottom of this article )

Question: replaced air conditioner compressor, new syste is icing up

Question: My air conditioner compressor blew, the new system is icing up, what's going on? add another return to it .

may have to change duct size maynot if indoor unit is close to returns . hope that helps a bit - Chris 3/15/12

Reply:

Rooster said:

Sounds like you may have put a 1500HP Blown Hemi in a Volkswagen. One thing to try...did the installer select the proper fan speed for the air handler? If the fan is running in a slower speed (usually for heating, not A/C), air flow will be inadequate. But I'm betting on inadequate duct capacity.

Probably should have stuck with the 4 ton evaporator coil. Sounds like an oversight or ignorance on the installers part to me.

Also see COOLING COIL or EVAPORATOR COIL for our article on causes of cooling coil ice problems. Something as simple as a dirty filter or blower fan can cause the trouble.

Question: my central AC unit is blowing out black particles

My central ac unit is spewing out black particles. I got the blower and the duct cleaned for my whole apartment, but the ac is still blowing the black particles. Does anyone have any idea what it is and how I can get rid of it. Thanks - Amsa 5/6/12

Reply:

Amsa: about A/C blowing out black debris particles, check for damaged duct insulation, say from a mechanical cleaning operation, and of course be sure you've got a new clean air filter in place; The inspection in the air handler ought to include a check of bearings and moving parts for damage;

Question: My A/C capacitor burned up

My capacitor on my Trabe XL13i burned up along with all the wiring above it into the compressor area, it appears to have caused a fire, because it melted part of the outside of the unit case.

Is it worth getting the wiring fixed and seeing if the rest of the machine still works or should we just call it quits and replace it? The air conditioner is 9 years old. - Shana5/16/12

Reply:

Shanna, about a burned up capacitor: it is possible for a capacitor to itself be the point of a failure; I'd try replacing the capacitor and any questionable wiring or connectors; let us know how that works.

Question: no cool air is blowing inside the house but outside compressor unit is running

No cool air blowing inside the house. The fan running outside is blowing cool air not hot/warm air. Not sure if it's a compressor issue. - Orios 5/29/12

Reply:

Orios, if the compressor motor never runs, but the air handler unit is running and the thermostat calls for cooling, the problem is at the compressor / condenser unit. See the diagnostics under "COMPRESSOR & CONDENSING COIL, A/C" (article link at the ARTICLE INDEX the bottom of this article )

Question: my 15 year old central air conditioner is running fine but I was advised to replace it to avoid risking refrigerant line contamination if the old compressor fails

I have 15 years old central AC unit. It is working fine. I was advised to replace it with a new one because there is a danger of refrigerant contamination of pipes if the old unit fails. If it happens,
to clean/replace pipes would cost additional 2000 dollars. How serious is it? - Salve 5/31/12

Reply:

Salve I think you should get advice from a different and more experienced HVAC tech. Like many a good lie, this one has some truth in it: if a compressor motor fails, burned oils in the refrigerant can contaminate the refrigeration piping - that's why when a burned out unit is replaced the tech will pull a vacuum on the system, do his/her best to clean the lines, and a special compressor burnout-filter or two will be installed on the refrigerant lines to protect the new motor and other parts from damage or debris clogging.

But a system can fail in a variety of ways, and as I explained there are well known means of dealing with debris in the system. What you were told would make me look elsewhere for my HVAC maintenance and repair services.

Question: My air handler works but the outside AC unit doesn't come on all the time - bad compressor?

my air handler works, but the outside ac unit does not come on all the time.

It's intermintent. My HVAC guy did pressures and said I have a bad comprresser (20 year old unit) and I'm better off getting a new ac unit. Sometimes it will come on and stay on. Other times it will not come on at all. - JPI 6/16/12

Reply:

JPI, I'm in no position to second guess the expert who was on the scene - s/he sees clues and performs test way beyond what we can do in a text Q&A. But here are some thoughts:

a failing compressor motor can become increasingly hard to start; the tech can install a hard-start capacitor to get the motor running again - for a time - and it might be worth a try: that's an inexpensive part and usually fairly straight-forward to install.

Question: 8 year old TempStar Air conditionre troubleshooting

We had a service tech out for a inspection check up of our 8 yr old tempstar unit because we cannot seem to get the the house temp to the low 70s even when unit runs for 5+ hrs strait....
the tech said the coil needed cleaning or replaced and our compressor was not starting and that it was just humming & clicking when trying to start and recommended to us 2 options to remedy the problem...new compressor or new system and both were not cheap.

while he was testing the equip outside I was in my office and could hear and feel the vibration of the unit trying to start...

My son-in-law came over and we removed the coil and cleaned it thoroughly and then checked all the wiring on the outside unit compressor and found a green wire disconnected and stuffed into a hole (Hmmmmm!).
we reconnected the wire and fired the unit up and the compressor seemed to start with no problem ( no humming or clicking).

So, if it is 98F outside we cannot get the inside house temp below 79f,,I put a refrigerator thermometer in front of an air duct and left it there for 30+ minutes and then checked it....it read 61F...I am at a loss of what to do....also the blowing air pressure does not seem to be strong.......what to do??? - Doug S 6/24/12

Reply:

Doug the green wire is probably a ground that needs to be connected, but I'm doubtful that that will fix a humming compressor -

more likely the compressor start/run capacitor is bad or the compressor motor itself is bad. It sounds as if there may be some risky do-it-yourself work going on - I'd call a trained HVAC tech at this point.

Question: metering device for refrigerant needs to match the condenser size (and evaporator coil size)

The metering devise need to mach condenser if is 4 ton set a 4 ton metering devise even on a 5 ton evaporator. - Anon 7/11/12

Reply:

Agree, though some TEVs can be adjusted within an operating range for most equipment in residential applications

Question: starting capactior uF microfarad measurements & tests

I am troubleshooting a 7500BTU Danby portable air conditioner (the tall vertical unit with ducting out the back via flexible hose). It appears that the compressor itself is at fault, but I would like to be sure before replacing the unit.

The start capacitor measures OK (meaures 46uF for a 45uF +/-5% unit) and appears in good condition. I measured the resistance between the three compressor terminals and they seem to be OK (C-S=2.8ohms, C-R=1.0ohms, S-R=3.7ohms) and there is high resistance between all terminals and ground.

I applied 117Vac directly to the compressor (bypassing the control circuits) and the compressor just hums - the current draw was 30A. Being a protable unit, everything is jammed into the compartment and I don't see any way to access the compressor at all. I'm about to give up on the unit and look for a new one,

but just wanted to see if there are any other things to try. The unit is probably about 9-10 years old, but has only seen regular use in the summer over the last 3 years.
Thank you for any help or advice.
Mike - 7/14/12

Reply:

I agree with your suspicion about the compressor. Often though a tech will just try swapping in a new start/run cap as a cheap simple test.

Question: air conditioner just blows hot air

air conditioner blowing hot air - Ann 8/4/12

Reply:

Ann,
with just the info you provided - blowing hot air - first make sure your thermostat is set to COOLING mode - and presuming it is and that all of the equipment inside and out are turned on, check

DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP

the article link found at the ARTICLE INDEX the bottom of this article - for a starting point in diagnosing why an air conditioner is not working.

Question: split system air conditioner stopped working - electric wires keep burning up at the terminals

My AC split unit stop working ,because the terminal wires connecting the compressor to the capacitor always burn this happen several times ,and the remedy was to replaced the burned wires,please can you advise what the reason that keep the terminal wire burn, the compressor is newly installed, Mohamed al lababidi -8/29/12

Reply:

Mohamed,

If the terminal wires keep burning up I suspect that the problem is one of

- an overcurrent - high amps draw because a motor is seizing and needs replacement - most likely it's this problem

- bad electrical connections, possibly involving alumnum wiring or loose connectors
- improper electrical wiring - such as undersized wires for the length of run, or mis-placed connections
- abnormal voltages in the system or voltage surges

Question: zero resistance test on AC compressor wiring

(Feb 11, 2014) Jerry Walch said:

I have always thought of this site as providing accurate information and have used it as a reference when writing technical articles. I'm having second thoughts.

This (Zero resistance: If there is zero resistance the winding is open or broken) mistake appears in this article on How to Diagnose & Fix a Burned-out Air Conditioning. Zero resistance indicates a short circuit not an open circuit.

Reply:

Jerry,

You are quite correct that zero resistance means a connection is made and good, not open and broken' infinite resistance would indicate an open circuit. We've published nearly five thousand technical articles and are grateful for careful readers who occasionally find and help us fix a mistake. I trust that an error that slipped by in an article would not be enough to toss out the work of our many editors and contributors.

We welcome content critique, corrections, or suggestions by this comment form or by email. I have corrected the text, added a warning, and would welcome further comments.

We've included a thank-you to you in our References section at the end of this article, keeping your ID private - let us know if you want to be identified by name in that part of the document. Thanks again,
Daniel

Question: AC compressor dead short to ground - rusty start capacitor

(Mar 7, 2014) Ricky Thompson said:

I recently had a compressor failure on my homes heat pump, the warranty sent a rookie out to inspect it. When the repair man shows up he asks me what kind of system I had, i told him a Trane heat pump. He then tells me he knows nothing about HP's.

Anyways he tells my warranty company that the start capacitor is completely rusted which is untrue it is rusty on top but surface rust, he also tells them that lady bugs and spider webs shorted out my board and tells them and improper installation of the cover let the water in to rust the cap. The cap tests fine, will this cause my compressor to short out?

The compressor is dead short to ground.

Reply:

Ricky I'm not sure about your message, but in general if a compressor measures as dead shorted to ground it's time for a new one;

the compressor motor windings might burn out if the unit could not start because it lacked a working start capacitor. I'm curious about the capacitor test involved; in any case the compressor windings could short independent of the capacitor status as well.

Question: causes of repeated AC or heat pump compressor burn-out

(June 1, 2014) Voscar said:

I got unit complit burn, all the wire, contactor, i rewire the all. But i notes at list that is the 3'time happens. Firts time i believe the 30 amps breaker never open because, i can. See one left was burn in the electrict box. Somebody put two separate breaker each 20 amps. Is how i finded. I revomed does breaker instead i put only one of 30 amps.

This time the breaker wont open. But the main breker outside open, only one side i still got only 120 in the place instead 240. I disconect the unit sistem. To fixed that. Why only would open the breaker in one side. Not complit.

Reply:

Repeated compressor burn-out certainly means that there is another problem with the system that has not been found.

In addition to the burned out compressor you have faulty circuit breaker(s) that need to be replaced: tell me the circuit breaker and panel brand and I can comment further.

But the compressor burn-up is probably not caused by the circuit breakers but by an operating problem in the system - improper charge, setup, or control board. Possibly low voltage or a start capacitor problem.

Question: how do I know if a new AC or heat pump compressor is really needed?

(June 3, 2014) Dana said:

I have a 22 yr old 3 ton Goodman unit at my home in Dallas, Tx. It recently stopped cooling the house although the inside fan & outdoor unit seemed to be running fine. There was some cool air blowing inside but not enough to cool the house & temps inside kept increasing.

Didn't seem to be blowing as hard as normal thru the inside vents either. Turned unit off since it was doing no good anyway & to prevent possible additional damage.

Nothing was iced up on the outside unit and there was no moisture on visible lines.

Prayed it just needed a Freon charge since I had just cancelled my AHS 1 month prior(Murphy's Law!). Friend hooked me up with a friend of theirs who works for AC company but moonlights on the side since I'm presently out of work.

Guy comes out, tests something on side of house that is connected to outside unit then opens the side of the unit, tests a few things with a metering device & immediately says my compressor is shot. Shows me a wire running from compressor that is burnt up on the end as evidence.

I read that a clanking noise is a sign of compressor going out & it has been making a clanking noise for a while.

Guy recommended replacing entire unit as the most cost-effective way to go since replacing the compressor, cleaning coils, etc would be almost as much as new unit. Said he can get the new unit with his discount for approx. $1,000 & will include warranty. Is he taking me for a ride or does he sound legit? Thanks in advance for your feedback!

(June 19, 2014) ken said:

bad compressor on 22 year old unit should i replace entire outside unit or just the compressor

Reply:

From what you describe I think the that you probably do need a new compressor/condenser unit.

Reader follow-up

Thanks! That's exactly what I did =)

Question: shorted, melted wires on Goodman AC unit

(June 19, 2014) Nick said:

I also have a Goodman central air unit. It was running fine but the wires going into the compressor corroded and shorted and melted the compressor terminals.

My plan is to replace the compressor. Do I have to worry about burnt freon? And also my model H23B223ABCA compressor is obsolete. There is a replacement for it but do you know if I will have to change any of the plumbing?

Or should it be pretty much plop it in kinda thing? I plan on having a tech doing the work.

Reply:

Nick,
The compressor replacement process should remove all refrigerant, pull a clean out vacuum on the system, and include burnout filter-drier canisters on the refrigerant lines to protect the repaired system.

For a bad compressor burnout some techs return a year later to replace the filter-drier canister once again. Going all that you should be ok.

Question: loud compressor noises

(July 5, 2014) dan said:

my heater started making a loud noise while the air conditioner was running , the air unit stills runs but no air comes thru the vents and the heater makes all kinds of noise

Reply:

Dan

Watch out: I would TURN OFFall electrical power to the system promptly to avoid further damage or hazards.

It sounds as if the blower assembly is damaged.

Question: circuit board replacement on AC unit, now compressor needed

(July 14, 2014) Wendy said:

Second repair call in a month. First, not cooling--a board needed replaced, no additional freon added. Now HP compressor has a short and needs replaced.

Trying to determine if it is better to replace entire outdoor unit. What are the chances that other components were damaged due to whatever caused this short before the unit started popping the breaker, whether from a power surge or attempting to run without enough freon or whatever?

Reply:

Wendy

Indeed the compressor is such a large part of the cost of the compressor/condenser unit that often it makes sense to replace the whole unit of an older installation.

But we'd be more comfortable with some report on the cause of the compressor failure. For example a power surge may indeed have damaged other controls & parts.

Question: AC runs but air not cool at all registers, "blown to ground" (i.e. a short circuit)

Aug 8, 2014) Jennifer said:

Hi. My AC was running but not blowing at every vent and air was cooler on some vents then others . Technician saw ice and then came back and did a leak test and found no leaks. Then AC worked for a day but began to turn on and off periodically . Technician came back out and AC compressor turned on and off while he was here.

He put a booster on it and cold water because it was hot and then tested something and said it was blown to the ground. Home warranty won't pay for blown to the ground diagnosis.

But it wasn't blown to the ground initially....right? Just trying to figure out if this makes sense or if warranty company is trying to get out of it. Thanks for your time.

Reply:

Jennifer

If the evaporator coil is icing over the system is not operating properly and may be low on refrigerant ( a leak someone has not yet found) or may have a failing refrigerant metering device.

Iced over coils can indeed also reduce air flow - but ALL of the air flow would be reduced not just air at some registers.

So I'd also look for open, loose, leaky, disconnected ductwork.

I have no idea what was meant by a "booster" added to the air conditioner, I don't know what "blown to the ground" means, but that sounds a bit like a short circuit and maybe the addition of a start capacitor to a compressor motor.

IF the AC compressor motor is not starting normally it may be damaged, at or near end of life.

Question: why does a blown compressor motor burn out wires?

11/13/2014 Deddy said:

About compressor burn out, i have outdoor unit Daikin VRV III RXQ16PAY1 and the compressor was burned out at cable lug compressor. how can it possible happen? (sorry for bad english)

Reply:

Deddy, a failing compressor motor can draw very high current (Amps) that in turn can certainly show up at a wire connector.

This is a companion article for COMPRESSOR / CONDENSER DIAGNOSTICS.

For diagnostic questions focused specifically on the outdoor condenser unit fan or fan motor, see FAN, COMPRESSOR / CONDENSER DIAGNOSTIC FAQs.

You may also want to see REPAIR & DIAGNOSTIC FAQs for A/C.

Question: compressor just runs for a few seconds, then cuts off; short cycling A/C compressor problems

My condenser starts for a few seconds then cuts off cycle continues - Anon.

my compressor fun has started to short cycle, it run for 2-3 min then shuts off for one second then restarts runs again then stops etc. with no funny sounds or noises - Don

Reply:

It's not clear from your question where in the entire cooling system your unit's troubles begin, so I'd look at diagnostic tips that may explain your compressor/condenser short cycling are found at LOST COOLING CAPACITY.

Certainly a compressor that is having trouble starting can be diagnosed at HARD STARTING COMPRESSOR MOTORS, if you're sure the trouble is outside.

Question: ice on the refrigerant line, no cooling in the house

My line set going to outdoor unit has ice on it. Lost cooling in house. What is the problem and is there anything I can do to fix the issue - Pat

Reply: check the indoor air handler for an ice-blocked coil

A problem with a refrigerant metering device (thermostatic expansion valve, capillary tube, etc), or even a dirty air filter can lead to improper metering of refrigerant into the indoor cooling coil, leading to icing; but other causes of ice formation include an improper refrigerant charge or even something as simple as missing refrigerant line insulation. But when you also lose cooling inside, I suspect an ice blocked coil.

See FROST BUILD-UP on AIR CONDITIONER COILS

Question: ice build up inside the ductwork

I have ice build up on the inside of the furnace duct work. This will plug up the lines and the fans will not circulate thus stop blowing cold air

Reply:

If you find ice build-up inside the ductwork itself that's pretty unusual except in winter in freezing climates when moist air is rising into the duct system. Usually ice forms at the cooling coil in an air conditioner air handler or blower unit.

But I agree that ice can block air flow and more, when it melts, can cause water damage or even a mold problem in the building.

For more detailed advice please see WATER & ICE IN DUCT WORK.

To diagnose and fix ice formation on the cooling coil itself, see FROST BUILD-UP on AIR CONDITIONER COILS

Question: My A/C unit kept blowing a fuse, now nothing runs

My Center A/C unit had a tuned up. I clean the evaporator, I put the blower down and put the new motor and clean the blades deeply, I have a clean filter, I clean the condenser deeply, and I bought a new thermostat. OK. The unit star running normally and you fill the normal warm air in the fan (outside) But 3 to 5 minutes later the heat in the condenser air increased suddenly the condenser stop with noise, and I need to turn it off. what is this? Please give me a clue? - Anon 6/28/22

I have a pretty old Tappan unit, and when the power goes out, if the A/C is running it will blow the fuse, usually we just replace the fuse, and now nothing will run on the A/C unit. any ideas? - Shantel 6/20/11

Reply:

Shantel:

Often when an A/C unit keeps blowing the fuse it's a sign that the compressor is drawing high amps which means it's jamming which, I'm sorry to say, means it's at end of its life. I'd have a service tech look at the unit; it might limp along for a while longer if s/he installs a hard-start capacitor kit.

When "nothing runs" you may have meant that the fuse or breaker tripped enough times that you've lost power on that circuit.

Anonymous - from what you describe you need a service call from a trained HVAC tech.

Question: My hi line is cold, low line is warm and the condenser blows hot air

In my situation the high pressure line is colder than the low pressure line.

The condensor coil blows mainly hot air, but the end closest to the compressor blows hotter air than the end furthest from the compressor line. Any suggestions? - Jim T. 7/13/11

Reply:

Mundo suggested: hey jim t check for restriction at the evaporator

Jim T:
Also, is your unit a heat pump or only an air conditioning system? - Editor. Let's be sure your system is in cooling mode.

Question: water comes out of my system when I turn on the A/C

When i turn on the (AC Outside unit Lennox ) there is an overflow of water in my basement at the furnace which is a gas furnace- Don 7/24/11

Reply:

Don if you see water in your basement at the A/C unit when it's on, your condensate drain or pump is not working.

Question: No water is coming out of the condensate drain

water is not going through the drain hose - Anon 7/20/12

Reply:

Anon:

If you don't see condensate coming out of the condensate drain there are several likely explanations:

- the drain system for condensate has become clogged - you need to clear the drain line - check this first

- the system is off or not in cooling mode so not producing condensate

- the air is dry enough in your environment that not much condensate is being produced

- your system uses a condensate pump that has lost power or failed

Question: Is the problem with the fan motor or the compressor motor in my condenser unit?

I've a Lennox outside a/c unit. The fan/motor and compressor are part of the unit. The fan was not spinning and the A/c is not running.

I've isolated the problem down to the fan/motor or the compressor, but don't know how to check or find out which it is. Any idea on how to check if the fan/motor is 'bad' or the compressor is 'bad'? - Fan or ... 7/23/11

Reply:

Fan or compressor: you could also have a bad control board, or relay switch in the compressor/condenser unit. If the fan is bad and the compressor is OK you'll hear the compressor turn on at the start of a cooling cycle, though a bad fan and system overheating could later cause some compressors to turn themselves back off. Similarly, if the compressor is bad your fan motor would still run. So I'm suspecting a control or switch problem./

Question: Our new AC won't keep running

uhm my A/C compressor broke about two weeks ago, we got a new one but when the fan starts the compressor works for a while and then it shuts down, and its turning on and off and i dont know whats wrong - Help. 7/25/11

Reply:

Help: if your new A/c won't keep running after it has just been installed, surely you should call the installer and expect it to be repaired under warranty - it's just been two weeks.

Even if all of the new equipment is in good condition, an example of a problem that could occur during compressor replacement is that contamination, moisture, dirt in the refrigeration system (which is made worse if a compressor burns up) can interfere with proper system operation.

Question: My AC won't work if I set the temperature down below 25C

my a/c is working properly when it is adjusted at 25 degree temprature, but if it is lower than 25, the compressor is disconnected by the overload protection. what is the problem with my a/c. - Mohamed 8/5/11

Reply:

Mohamed an A/C compressor may cut off on thermal overload due to overheating from local conditions around the compressor/condenser unit (no shade, very hot weather), an older motor that is failing, a start capacitor problem, or even a refrigerant metering device problem. If there's nothing obvious to you, I'd get a service tech to take a look. Keep us posted.

Question: Icing at the compressor; compressor not turning on?

the outside unit of the heat pump is icing up on the compressor - Steve 8/7/11

Hi my fan in my house goes on but my compressor unit does not all the electric seems to be fine . could it be my thermostat? - Sam 8/7/11

the accu very heat,although it is new gen. clean,2Tr LS-60psi & HS-100psi, - Anon 8/6/11

Reply:

Steve: icing at the compressor/condenser sounds like a refrigerant charger or refrigerant metering problem.

Sam: if your thermostat turns on the air handler but the compressor/condenser does not run, the problem is not the thermostat. Check out the diagnostic suggestiosn beginning at LOST COOLING CAPACITY (link at the ARTICLE INDEX the bottom of this article )

Anon: those pressures look kind of low, no? What does your HVAC tech say about normal for that system?

Question: My A/C compressor just won't stop running

I recently noticed my AC condenser unit still running when the system inside shutoff by itself. and also, does the condenser unit have to be leveled. I notice the slap which holding the unit is slopping. Any suggestions? Thank you. - Rick 8/16/11

Reply:

A/C compressor/condenser won't stop running:

Rick usually when an A/C condenser unit won't stop running even though the inside equipment has shut off by itself my thinking divides into two investigations:

- is there a problem with the INDOOR unit such as a blower fan that won't start, an access door switch open, a condensate drain switch turning off the blower unit - these can leave the system calling for heat and the compressor running (though that's not good for the compressor)

- is there a problem with the outdoor equipment such as a bad control relay or control board

Question: can the condenser get oil logged

can a condenser become oil logged, how and why? - Dominic 8/22/11

Reply:

Dom, it is normal for some refrigerant oil to circulate through the HVAC refrigeration system; Oil logging can occur in some installations if the refrigerant piping is not properly routed or due to an improper charge. The more usual problem is not at the condenser coil but at smaller orifices such as a cap tube or the TEV.

Dominic:

A condenser, if you mean the condensing coil, set level, would not be expected itself to become oil clogged, though condensers do sometimes clog from a combination of debris and moisture or oil.

But refrigerant oil moving through the system can clog a refrigerant metering device such as a capillary tube.

Question: compressor starts, fan doesn't start, I hear a hissing

My compressor turns on but the fan does not turn(Ican turn the blades by hand) within 10 t0 15 seconds I get a long a loud hissssssssssssssssssssss.
Thanks foir you help
Henry - 9/8/11

I have some more info on my a/c when the a/c is turned on by dropping the temp in the house the compressor turns on but the fan does not turn, if you start to turn the fan by hand it starts spinning. When i turn it off by picking up the temp it stops. When i drop the temp again nothing goes on. If i wait a few minuites and try it again the compressor starts but the fan still has to be started by hand. Thanks for any help you can give

Reply:

Henry I suspect a bad fan start-run capacitor.

...

Continue reading at COMPRESSOR / CONDENSER DIAGNOSTICS - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see COMPRESSOR / CONDENSER DIAGNOSTIC FAQs-3 - more-recent Q&A about troubleshooting the A/C compressor-condenser unit

Or see these

Recommended Articles

• BURNED-OUT COMPRESSOR
• CAPACITORS for HARD STARTING MOTORS to try to kick start a reluctant compressor motor
• COMPRESSOR / CONDENSER REPAIR - home

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