Air Conditioning & Heat Pump FAQs

Questions & answers about fixing problems with air conditioners & heat pumps posted by readers at the A/C or heat pump diagnostic home page.

Fourth set of A/C & heat pump questions & answers.

Air Conditioning & Heat Pump Troubleshooting FAQs-1

These questions & answers about diagnosing trouble with air conditioners and head pumps were originally posted at AIR CONDITIONING & HEAT PUMP SYSTEMS

A good place to look for diagnostic procedures is DIAGNOSTIC GUIDE A/C or HEAT PUMP.

Also see this series of A/C & Heat Pump Diagnostic FAQs sorted by major topic area are given at AIR CONDITIONING & HEAT PUMP SYSTEM FAQs

On 2011-07-09 by (mod) -

I agree that a bad contactor relay could also prevent a compressor from running, but I suspect that burning A/C controls, switches, contactors, or circuit breakers will often be traced to a compressor that is seizing and drawing high amps.

On 2011-07-09 by TN-Goose

Jeremy: What does the contactor look like, and where is the push button you're referring to?
I'm wondering if my outside compressor/condenser unit has similar problem where the fan runs at half speed even when the indoor thermostat is switched OFF.

On 2011-07-09 by Jeremy - I could manually push in the single button to start the compressor and fan manually.

Last week, I woke up to the indoor temperature a few degrees high. Warm air was blowing in. I went to my outside unit and the fan was not running. I replaced the capacitor and it worked. But the air conditioning couldn't keep up at night. During the day when it was around 99 my home was nice around 76 but at night around 81.

Yesterday the compressor was not running. It was getting power. Today, I put in a hard start kit and it worked. But about five hours later the compressor was not running, just the outdoor unit fan. I pulled the power and when I powered up again, even the fan and compressor did not start.

Multimeter showed me around 25V on the two lines coming from indoors on two sides of my contactor (and 120 V on the other two connections). One of the 25V lines connected to the two sensors on the refrigerant lines. But the contactor didn't engage.

I could manually push in the single button to start the compressor and fan manually. What would cause three different issues within one week? I plan to replace the contactor tomorrow. Another night of muggy 90+.

On 2011-07-09 by TN-Goose

I replaced the 50/3 MFD capacitor with a new one. Noticed the outside compressor fan running at half-speed as before when the indoor TT is set to OFF (yes, it's baffling).

As soon as the indoor TT was switched to ON, the fan spun to full speed, then the 30Amp breaker tripped immediately (maybe due to compressor malfunction).

Was hoping the new capacitor would resolve the issue, but looks like seized compressor and/or a bad controls in the outdoor compressor/condenser unit as you mentioned. Thanks again for your help.

On 2011-07-08 by (mod) - A lack of coolant will not stop a compressor motor from running

A lack of coolant will not stop a compressor motor from running, the motor will run but if there is too little or no refrigerant gas (in your case Freon R22 which is obsolete) the system just won't cool the air blown across the evaporator coil.

You need a new compressor if the old one is seized or if it is so worn that it won't compress the refrigerant gas. If your system is not cooling because it's lost refrigerant, it may be possible to re-charge it. Ask for specifics of how the tech knew the problem is the compressor.

On 2011-07-08 by Ken

I have an A/C system that is no longer cooling. The serviceman came out and said we needed a new compressor. he stopped by to drain Creon/r22 or what ever cooling agent but said there was none in the system. Can a lack of cooling agent stop the compressor from running?

On 2011-07-08 by (mod) -

Dana asked :My A/C drip pan over flowed and water ran all over the unit. We have cleaned the clog but now the unit inside will not start. The fan is turning outside.

Some A/C condensate pans use a water sensing float switch to turn OFF the system if the condensate overflow pan receives water - that's to force the occupants to find and fix the problem. If that switch was damaged, tipped over on its side, or clogged with crud it could be leaving the air handler switched OFF.

On 2011-07-08 by (mod) - window A/C unit blows only hot air

Mary if your window A/C unit blows only hot air I suspect that either it has lost refrigerant or the compressor is not working; a low but not totally lost refrigerant level can also cause icing on the condenser coil in the unit that would make it stop cooling. IF the unit sometimes blows cold air and sometimes only hot air, I suspect icing and a low refrigerant level.

On 2011-07-08 by mary f howard

i have a regular apartment window airconditioner, and some times it blow out hot air,why?

On 2011-07-08 by (mod) - "If the compressor is rated for 14Amp and is running at 11.8 Amp dose this mean the compressor is ready to burn out?

Jim:

About your question "If the compressor is rated for 14Amp and is running at 11.8 Amp dose this mean the compressor is ready to burn out?"

Not in my book. Usually when a compressor is seizing up it will draw abnormally high amps not lower amps. Take a look at the RLA figure for your unit.

On 2011-07-08"If the compressor is rated for 14Amp and is running at 11.8 Amp dose this mean the compressor is ready to burn out?by (mod) -

Tony: did you check the TEV (Thermal expansion valve) ?

On 2011-07-07 by tony

im working on a coolair spilt unit with 2 evaporator's 1condenser and 2 compressor's all fan belt's and condenser belt are good .

all filter's were changed ,one of the evap section is discharging 55deg air at 86deg outside temp and gauge pressures of 65/245 and the other evap at 86deg out side temp is discharging 64deg with pressures of 78/265 can you help .

On 2011-07-07 by Colleen

Thank you, I will read the Apedia on "fan limit switch". We thought it might be the thermostat and replaced it twice. Replacing this did not change the fan staying on problem.

On 2011-07-06 by (mod) - if your indoor air handler fan won't turn off,

Colleen: if your indoor air handler fan won't turn off, either the thermostat is never being satisfied or someone has set a switch to run the fan continuously (or thermostat control wires shorting together are causing it to run)

In addition to the "fan on" switch on some thermostats, the fan limit switch found in the air handler of many systems includes a white button that can be set to make the fan run full time. Search InspectApedia for "fan limit switch" to find the article describing that device.

On 2011-07-06 by Colleen

my fan is set on auto, and the inside fan will not cycle off. the outside unit cycles on and off thouth the inside fan will not. It use to. It is like someone set the thermostat fan to the on position. Even in the auto position the fan never turns off. The house is cool and everything else is fine. What would cause this?

On 2011-07-06 by (mod) - drop of refrigerant oil hanging off of the high pressure side

Brad: "drop of refrigerant oil hanging off of the high pressure side" could mean you have a refrigerant leak at that fitting.

And yes the small canister is usually a water filter installed on a line when a system has had to be opened for service.

On 2011-07-06 by Brad

re: additional info to my last post. The airflow is very good. The air filter is good (pleated type), no obstructions. Just noticed a drop of refrigerant oil hanging off of the high pressure side between a small canister I assume is a filter and the expansion valve. Thanks

On 2011-07-06 by (mod) -

THANKS to TN-Goose for helping reply to A/C questions in this forum.

On 2011-07-06 by Anonymous - low overall cooling capacity"

Brad: re: "low overall cooling capacity" you didn't indicate if the air flow volume is low or the air flow volume is ok but the temperature of the air supply is not cool enough. That distinction is not a bad place to start diagnosing air conditioning: low air flow points to dirty filter, blocked or disconnected ducts, a closed register or damper, blower problem, air leaks etc. Air supply that is not cool enough points first to a refrigerant loss or a comperssor condenser problem.

Tom:
The temperature of the supply air at a register should be quite cool, much cooler than room temperature, so comparing it with the setting or reading at the wall thermostat won't be a very clear diagnostic. I'd start by looking at the article above where we discuss what things to check first if your air conditioner is not cooling adequately. If none of those leads you to something obvious that a homeowner can fix, like a dirty air filter or a disconnected air duct, you'd best call a service tech.

On 2011-07-06 by Brad

I have a 3 year old lennox hvac system (Complete new system ductings etc.). Currently experiencing low overall cooling capacity. Condenser is clean, fan blowing, compressor pumping. However, both high pressure and low pressure are cold either at condenser or coil. Air filter is clean. Any ideas? The contractor that installled unit is no longer in business. Thanks

On 2011-07-06 by Tom

It appears that my air may be loosing its cooling effect. Without calling a service tech, can I measure the cooling at a vent and compare to wall thermostat?

On 2011-07-06 by TN-Goose

To Jennifer:
If your compressor is indeed in need of refrigerant, make sure you find out why the refrigerant leaked and have it addressed before you recharge the unit with refrigerant. Otherwise, the refrigerant will leak out again over time.

To Jennifer:
Is the fan running on the compressor/condensor unit? If your compressor and fan are running fine, then possibly it's out of refrigerant.

On 2011-07-03 by al entez

why am i getting return air for my hvac from garage ceiling .air is so hot in garage area

On 2011-06-28 by Jennifer

In our home we have two outdoor compressors. One for upstairs and one for downstairs. The downstairs unit is cooling fine. However, the upstairs unit is blowing lukewarm air. The compressor is running fine there just isn't any cool air coming out of the upstairs vents. Any ideas?

On 2011-06-27 by sherry

My air conditioner works great for awhile and then the cold air stops coming out and the air temp starts to rise. The outside fan is still running. Can anyone help?

On 2011-06-26 by gene

my ac is cooling fine but the blower fan wont cut off when its time any suggestions

On 2011-06-25 by ronnie e mills - the condenser unit was burnt out

i went to this job site and found out that the condenser unit was burnt out unit came up but not enough air is coming in the building the second compressor will not come on york 3 1/2 ton

On 2011-06-25 by Denver - HVAC by Carrier, when my a/c turns on it sounds like the heating unit also lites.

I have a HVAC by Carrier, when my a/c turns on it sounds like the heating unit also lites. is it really trying to run both heat and a/c ? if so how to fix ? turn off gas to heater? First time home owner, new to all this.

On 2011-06-22 by Tim

My A/C gives 20 degree drop in temp between return and supply on coolish days but on hot days I'm only getting about 5 degree drop.

Also, the pipe from outside compressor has NO sweating on hot days (when not getting enough cooling) but sweats as expected on coolish days (when getting enough cooling). Does my 10 year old compressor unit need repair or replacing or something else?

On 2011-06-22 by Dana

My A/C drip pan over flowed and water ran all over the unit. We have cleaned the clog but now the unit inside will not start. The fan is turning outside.

On 2011-06-21 by Joe

My ac is blowing air out nicely from the registers but the air is not cold enough. I touched the thin copper metal tube being fed into the unit and it was quite cold. The filter was clean. What could be causing the air not being cooled?

On 2011-06-21 by jim Hanlon

Jman the outside temp was over 95

On 2011-06-20 by jman

To jim no that the rating for design conditions was the temp outside 95 if not then it is good

On 2011-06-17 by jim

If the compressor is rated for 14Amp and is running at 11.8 Amp dose this mean the compressor is ready to burn out?

On 2011-06-17 by robert

thanksfor much info.. been a big help.. more power!!

On 2011-06-17 by TN-Goose

DanJoe: I posted this a few days ago....could you comment?
I removed the capacitor from the outside compressor/condenser unit. It's a dual 50/3 MFD 50/60Hz type, but no indication as to the +/-% MFD. The HERM side measured 44.5uF and the Fan measured 3.05uF. Does this mean the capacitor is bad?

I also checked the resistance of the compressor....terminals Red+Black=32.3 ohms, Red+Purple=2.8 ohms, Purple+Black=34.6 ohms. The same 3 color terminals measured individually to the body of the compressor measured as overload (O.L on my FieldPiece multimeter). Do these resistance reading indicate a bad compressor?

On 2011-06-16 by (mod) - press the reset button to get it going again

Re: "I have to press the reset button to get it going again. It doesn't run long before doing the same thing"

If a motor keeps going off on thermal overload reset chances are that the motor itself is failing and needs replacement. Something else could be causing the motor to overheat however, such as inadequate air flow when the compressor unit is blocked by shrubs or is located too close to a building.

On 2011-06-16 by (mod) - If no air is coming out of your supply registers

Mike:
If no air is coming out of your supply registers, the air handler is not working; be sure that there is power to the unit and the thermostat is properly set to COOL; if your thermostat has a FAN ON switch you can try to just force the fan on to see if the blower will work at all.

On 2011-06-16 by Mike

outside compressor and fan seem to be working fine, but no air blowing out of the inside ducts?? please help! thank you

On 2011-06-16 by (mod) - Hard start capacitors and motor start/run capacitors

TN-Goose & Andrew:

Hard start capacitors and motor start/run capacitors are discussed in detail beginning in the article found by using the on page search box to find CAPACITORS for HARD STARTING MOTORS

On 2011-06-16 by TN-Goose

To Andrew: while troubleshooting my compresson/condenser unit problem, I came across a tip that said that some special capacitor, called hard start capacitor, can be added to give a boost start to the compressor (especially older ones that are hard to start). It said the hard start capacitors are a combination of a capacitor and a built-in relay. Supposedly, they are inexpensive.

On 2011-06-15 by Andrew

There is no ice on any lines -- there not even cold. I went out there and turned it on again. But this time i lissened. I heard the compressor make a grr sound then a min or 2 later a grr sound again then never made noise after that. Anyone have any idea. My recent post is 6 days prior to this one.

On 2011-06-15 by kitt

I turn my thermostat to cool set the temp fan kick in but nothing turn on the air conditioner. I don't hear the fan kick in on the unit. We has a string of hot days. The ac would turn off but noticed when the night got cooler the ac was still blowing air but not cool and i didn;t hear the unit humming. I have someone comming tommorow just worried its going to be expensive meaning no air for me this summer.

On 2011-06-15 by Matt

There's no difference in which way the frequency (50/60 Hz) is stated. Some like to say it in numerical order: 50 before 60. Some like to say the more common one (60 Hz in the US) first with 50 Hz second (some other countries use 50 Hz).

On 2011-06-14 by TN-Goose - Would a dual capacitor specified as 50/3 MFD and 50/60 Hz be different than one specified as 50/3 MFD and 60/50 Hz?

Would a dual capacitor specified as 50/3 MFD and 50/60 Hz be different than one specified as 50/3 MFD and 60/50 Hz? For example, is there any significance to the frequency spec being shown as 50/60 Hz vs. 60/50 Hz?

On 2011-06-13 by RonniE K

During the day, my condenser stops running while the air blows warm inside. When I go out to check it what's going on, I have to press the reset button to get it going again. It doesn't run long before doing the same thing so I've been leaving it off mostly because it can't keep up with the 90+ Texas temps during the day.

The crazy thing... at night it works just fine (a cool 74). So between about 7pm and 10am I have AC but the rest of the day... it's hot. This has been going on for two weeks. Any ideas?

On 2011-06-11 by TN-Goose - terminals Red+Black=32.3 ohms, Red+Purple=2.8 ohms, Purple+Black=34.6 ohms.

I also checked the resistance of the compressor....

terminals Red+Black=32.3 ohms, Red+Purple=2.8 ohms, Purple+Black=34.6 ohms.

The same 3 color terminals measured individually to the body of the compressor measured as overload (O.L on my FieldPiece multimeter). Do these resistance reading indicate a bad compressor?

On 2011-06-11 by TN-Goose

DanJoe,
I removed the capacitor from the outside compressor/condenser unit. It's a dual 50/3 MFD 50/60Hz type, but no indication as to the +/-% MFD. The HERM side measured 44.5uF and the Fan measured 3.05uF. Since the HERM terminal measured below 10% of specified 50 MFD, the capacitor is no good. Do you agree? Do you know of a good source for purchasing this type of capacitor?

On 2011-06-11 by Brenda

My AC unit outside is making so loud noise and now it the fan is not moving and stop running. But the unit inside is running but it's not cold air.

On 2011-06-11 by Herb M.

Ice on the rrturn line at the condenser?

On 2011-06-08 by Andrew - 1995 York Steller H1DB Split system

Installed in 1995 York Steller H1DB Split system. First time since then had any problems with it. AC runs but no cold air and all lines to and from AC air normal temp. Used this site to help go threw my check list :) Ran into one problem -- I can't locate Condencer Relay or any relays what so ever Besides (1 Contactor) for the fan --

Or if even has one. I looked inside were the fan is, outside in panel, and took time to look in and around furnace. Do you have anyideas were my relays may be?

On 2011-06-08 by (mod) -

Thanks for the Kudos. We are dedicated to making our information as accurate, complete, useful, and unbiased as possible: we very much welcome critique, questions, or content suggestions for our web articles.

On 2011-06-08 by Livvy

THANKS FOR YOUR RESPONSE!
...THIS IS SO COOL!! Have to tell my friends about you!

On 2011-06-07 by (mod) - If your outside fan keeps running

Livvy:

If your outside fan keeps running it's possible that that's normal IF the compressor was working also during the night - under heavy continuous cooling loads the system might run a lot.

But if the compressor shuts down and the outdoor condenser fan keeps running for more than a few minutes I suspect that there is a bad switch or control board in the system.

On 2011-06-07 17:10:57.270791 by LIVVY

MY AC FAN OUTSIDE WILL NOT STOP RUNNING...SOUNDS LIKE MOTOR & FAN RAN ALL NIGHT...CAN WE RUN THE AIR LIKE THIS...WHAT WOULD CAUSE THIS TO HAPPEN AND HOW CAN IT BE FIXED?

On 2011-06-07 by (mod) -

Michael:
Can a refrigerant overcharge ruin an air conditioning compressor: sure.

I'm not expert enough to make a general comment about ALL AC compressors, but certainly there are some designs in which an overcharge that sends liquid refrigerant into the compressor piston or valve area can ruin it promptly. Imagine a piston trying to move in a cylinder that has liquid in it where just compressible gas is supposed to be found.

On 2011-06-07 by (mod) - a high amp draw on the compressor circuit

Thanks Richard for the followup A/C diagnostic detail. Indeed a high amp draw on the compressor circuit is one of the basic diagnostic tests that lead a tech to think the unit is seized or failing.

The high pressure (smaller diameter) refrigerant line is not normally cold in cooling mode but could be warm or even hot depending on where along its length you are checking on its temperature.

The low pressure or suction line (the larger diameter refrigerant line) is normally cold when the air conditioner has been running for a while and can even show frost on uninsulated sections.

I'm not sure from your description if I can say that the high pressure warm line is a problem, but if your low pressure line is never getting cold I suspect a lost refrigerant charge (or the compressor is not running at all).

On 2011-06-06 by Donna

my 3 yr. old high efficiency heat pump is set at 76 and past summers runs usually in dehumidify until it reaches the set humidity @56% and then the fan runs. this has been very efficient. this year it runs on LOW for 2 hours at a time then fan (it stays below56% humidity).

I noticed that the larger of the two copper pipes (inside and outside) are cold, this website says the other two pipes (I believe they hold the liquid stage puron)should be warm. These 2 pipes (one in, one out) have absolutely no temperature... is this a sign of a puron leak.

On 2011-06-06 by Richard - Compressor has failed mechanically (drawing far too many amps).

Just a follow-up for future readers. Compressor has failed mechanically (drawing far too many amps).

My no-name (builder grade) outside unit trys to start but won't. The fan runs fine (I replaced it last year)but the compressor tries to start for about 2 seconds, then stops. About 45 seconds later it will try again. Same results. It never trips the breaker.

I had a tech come out while I was at work and he "thinks" the compressor is locked up. I checked the resistance today and got .001 C-R, .002 C-S, and .002 R-S. My DMM reads OL (overlimit) when checking all three terminals against the compressor case. I'm leaning toward low refrigerant (is there a low pressure shut-off on home systems like in cars?).

Tech that came out told the wife it wasn't low on refrigerant but...? I'm gonna swap a known-good Run-start cap from my other unit and try that. I guess the compressor could've failed mechanically. Any thoughts?

On 2011-06-06 by Michael - air conditioning unit stopped working after being charged

My air conditioning unit stopped working after being charged 2 weeks ago (ran great afterwards).

After bringing out a different AC company, he said the last guy overcharged the system and the compressor was shot. He said he was certain of this because he found liquid refrigerant on the "gas side". Is this true? Is there no other way for liquid to be on the gas side of the system unless the system was overcharged? (Long story short, my landlord is trying to stick me with the bill because I called the first company to come out, which he had no used before)

On 2011-06-05 by TN_Goose

I'm going to check the capacitor MFD first, then if it's not the capacitor issue, I'm going to call Hiller Air Condtioning. I'll post the result of the root cause finding. Thanks again for your help.

On 2011-06-05 by (mod) -

Typically for the symptoms you described, if it's not a thermostat problem, the service tech will probably do some simple electrical tests of the compressor/condenser unit, check system pressures, and will visually examine the controls and circuits in the outdoor compressor/condenser unit for an obvious problem before doing more sophisticated tests.

FYI sometimes a capacitor can be bad without bulging.

Compressors can seize from internal wear, a problem that can be accelerated if there is moisture or if there are contaminants in the refrigerant.

On 2011-06-05 by TN_Goose

Thank you for the quick reply. When you say "bad control board or circuit", are you referring to the ones in the compressor/condenser or TT?

Would a faulty capacitor (one that might be almost ready to fail) cause the compressor fan to run? It's really odd for the fan to run with TT set to OFF. I opened the outer casing of the compressor/condenser today and checked the apprearance of the capacitor (looks fine..

.no bulging or corrosion anywhere...couldn't check for the MFD..waiting on the just purchased HVAC/R multimeter shipment), and all wiring connections from the compressor and the fan look OK (no shorting or loose connection). What would cause the compressor to seize or burnup? I'm wondering if the extreme hail storm and heavy rain that partially flooded outside compressor/condenser area (about 3-inches of water) has anything to do with it.

On 2011-06-05 by (mod) -

TN_Goose:
It sounds as if your outside compressor/condenser is not starting; a compressor that has seized or is drawing high amps would trip the breaker. I'm baffled about why the outside compressor fan would run at all when the indoor TT is set to OFF; could be a bad control board or circuit or one that was damaged during compressor burnup.

On 2011-06-05 by (mod) - If your A/C fan is buzzing

Jeff:
If your A/C fan is buzzing but not spinning my first guess would be that the motor is burned up or perhaps easier, the motor needs a starting or start/run capacitor. Under COMPRESSOR & CONDENSING COIL, A/C check out the article titled CAPACITORS for HARD STARTING MOTORS (see links(links found at the ARTICLE INDEX near the end of this page) ).

On 2011-06-05 by (mod) - pressure readings may indeed indicate that the compressor has lost an internal seal

Pahugh:

I'm not sure, but those pressure readings may indeed indicate that the compressor has lost an internal seal or has a bad internal valve. Before replacing the compressor you need to ask what refrigerant was used to recharge your system when it was last repaired. Putting a new A/C refrigerant into an older unit that was designed for a different refrigerant wont' work properly.

On 2011-06-05 by Jeff

My Goodman Janitrol 2 ton turns on but the fan just makes a "buzzing" sound instead of spinning.

On 2011-06-04 by TN_Goose

The outside compressor/condenser unit of my central air conditioner, which is wired to a bi-pole 30amp circuit breaker, started to trip the breaker whenever the indoor thermostat turns ON the air conditioner. Never had this issue in the past 6 yrs.

Despite the breaker being tripped, there's air coming out of the supply registers, but it's warm obviously due to the compressor/condenser unit being tripped OFF.

What could be some reasons for tripping the breaker? One strange condition I noticed is that when the indoor thermostat is switched to OFF (not on Cool), the breaker stays ON without tripping, and the compressor/condenser unit's fan rotates at about medium speed, instead of being OFF. Any suggestions or help will be appreciated.

On 2011-06-04 by Pahugh

Have Goodman home unit with R22 about ten years old. Compressor replaced 5 years, one month ago (out of warranty). Evaporator core recently replaced due to leaks, and unit has not worked properly since providing minimal cooling.

With outside temperature of 95, have head pressure of 210 and suction pressure of 118. Suction line is sweating at the core and outside but little cooling. I am being told that the compressor is bad. Could something have happened during the evaparator core replacement to cause this, or could there be a problem with the new evaporator core.

As the homeowner I am suggesting evacuating and recharge but this may be a futile exercise. Other causes have been ruled out (i.e. airflow okay, no freezing up, etc.)

On 2011-06-03 by (mod) - heat pump that works ok in cooling mode until late in the day when it shuts off

DH:
Your description of a heat pump that works ok in cooling mode until late in the day when it shuts off and is very hot makes me think that a motor, possibly the fan motor is overheating and shutting down on thermal reset. Some electric motors contain a built-in thermal overload switch that will reset itself automatically when the motor cools down.

If that's what is happening the motor could need replacement, or it may be that the compressor is in a very hot location and / or is not seeing adequate air flow. I see this problem when a compressor unit is installed too close to a building or when airflow in or out of the unit is blocked by a building wall or shrubbery.

It's worth a service call to have a trained tech look at the installation and motor. Let us know what you find - it will help other readers.

On 2011-06-02 by dh in texas

Here recently, my heat pump unit has started to act up. It tends to work well for the better part of the day.

The compressor will run and there is good cold air flow out of the supply registers. However, late in the afternoon (peak heat time) the heat pump fan will abruptly stop (with great deal of heat near heat pump fan). Restarting the system after a 30-45 minute "off" cycle will generally restore its operation. Any ideas?

On 2011-06-02 by (mod) - tech says I need to replace the compresso

Frank:

I can't second guess the tech who was at your site, but here are a few questions to ask:

1. What does "had a line in the whip cut" mean?

2. If the compressor is running and there is good air flow out of the supply registers but no cool air is being delivered, it could be a simple refrigerant leak that needs to be fixed followed by recharging the system. So I'd ask why that means a compressor is needed or why a whole system replacement is needed.

3. If the compressor is running and there is POOR air flow out of the supply registers but the3 air is cool, then the problem is with the blower fan, a blocked or iced evaporator coil, or disconnected, crimped, damaged ductwork, or even just a dirty air filter. So I'd want a more clear definition of just what's wrong so that you have confidence in the diagnosis and thus in the remedy.

Eric:

If air is blowing out at a good rate but is not cool, see my comments just above.

On 2011-06-01 by frank

I had a line in the whip cut. and now the tech says I need to replace the compressor. The compressor runs but no cold air is being circulated. He also said that I would be better off buying a new unit versus replacing the compressor. The unit is five years old at the end of the month. Your thoughts?

On 2011-06-01 by Eric

Hey , everything is running and air is blowing out all vents but no cool air, no coil icing, no water dripping in pan, and have a clean air filter. Do i just need a recharge of coolant?

On 2011-05-31 by Laura

Thanks, I'll update tomorrow after they visit.

On 2011-05-31 by (mod) -

Laura: I'm not sure what the "intake valve" is referring to. Certainly there are come controls such as the thermostatic expansion valve that meters refrigerant into the evaporator coil that are not so costly for the part, but because its replacement requires the time and labor to empty, vacuum, and then recharge the system, the total cost of the job can be several hundred dollars.

Ask the A/C repair company to be more clear on just what part failed and what's involved in its replacement. Let us know what you're told as it may permit further comment and/or it may help other readers.

On 2011-05-31 by Laura

I had my furnace replaced a couple of months ago. The A/C was in fine working condition last summer. When we turned on the A/C last week it wasn't working so we called the company that replaced the furnace to come out and make sure that it was all properly hooked up since the furnace was replaced

After inspecting it, they told us that the intake valve wasn't working and it needed to be replaced, at about $450. Does this sound a little fishy seeing that it was all working fine last summer? I feel like they are trying to take advantage of us. Any comments, suggested questions to ask or feedback would be GREATLY appreciated! Thanks!

On 2011-05-31 by (mod) -

Some causes of a home air conditioner compressor short cycling on and off too rapidly include these:

1. loss of refrigerant - a refrigerant leak in the system. You may be able to repair the short cycling problem temporarily by recharging the system but the proper repair is to find and fix the leak.

2. coil icing: the evaporator coil (cooling coil) is iced over (such as due to improper refrigerant charge or dirt or a reduced air flow due to a dirty filter) - take a look in the air handler to see if the coil is blocked by ice or dirt.

3. oversized air conditioner: if the short cycling has always been a problem since the day the system was installed, there is a good chance that the unit is too big (too many BTUS) for the space being cooled.

A more subtle version of this same problem is that you've done something like closing doors or adding a partition that had the effect of reducing the size of the space being cooled. Sometimes we can mitigate this problem by running the blower fan at a lower speed or by opening interior doors to increase the size of the space being cooled or even by moving the thermostat.

On 2011-05-31 by Joe

I have the same problem as Mather: my compressor cycles on and of every ~10 seconds. I is about 5yr old. What can we do to fix this system. Please help. Thanks!

On 2011-05-31 by carla

My outside air unit will not turn off on its own. I have to maually turn the breaker off to turn it off. Does anyone know why or how I can fix it?

On 2011-05-30 by matthew

Are compressor cycles on and of every few seconds or minutes. What can we do to fix this systems not even a year old

On 2011-05-30 by Amanda

I had my system gased up last week...$210! The unit is not producing enough cold air. The unit is set on 72 and does great at nights but during the day where the temp. ouside is reaching mid 90"s it's getting up to 80 in the house. Is my duct work screwed up? how do you repair trailor metal ducting?

On 2011-05-29 by Anonymous

Les:

A leak that was fixed by a re-charge is not as good a repair as a leak that was fixed by finding and fixing the leak - you'll just have to keep adding refrigerant.

But weak air flow out of the vents would not be due to a refrigerant leak; more likely a clogged filter or crushed or disconnected ductwork, or a blower fan problem.

On 2011-05-28 by Les

Our ac was serviced two months ago and the repairman said it had a leak. $400 later it was recharged with coolant and now the ac is doing the same thing. Very little pressure coming out of vents and no cold air coming out. Does anyone know what I can do for the weekend? It is stifling!!!!

On 2011-05-28 by (mod) -

JMONTE:
If the HVAC suction line gets warm, you may be out of refrigerant, or the system may be running in heating mode if it's a heat pump.

On 2011-05-28 by (mod) - motorized HVAC zone control damper is not opening or closing

If a motorized HVAC zone control damper is not opening or closing, most likely the motor has failed, or the thermostat that operates that zone control is off or set in an incorrect position.

On 2011-05-28 by Becky

my house has "zone" control with dampeners to close off the upstairs over the gargage room unless that thermostate is on - the room is not cooling. I have located the damper under the house. What are some causes for the damper not opening and how to repair them? condensation, motor to damper? silcon glued properly?

On 2011-05-28 by jay

cool website thanksss

On 2011-05-27 by JMONTE

after my condenser is turned on for about 4 minutes the suction line starts to get warm to the touch. can you tell me what the problem may be

On 2011-05-13 by jim

if filters are clogged will it cause the thermostat to shut off?

...

Continue reading  at DIAGNOSTIC GUIDE A/C or HEAT PUMP or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

HVAC repair guides

• AIR CONDITIONING & HEAT PUMP SYSTEMS - home
  • AIR HANDLER / BLOWER UNITS - home
  • BURNED-OUT COMPRESSOR
  • CAPACITORS for HARD STARTING MOTORS
  • CHATTERING RELAY CONTROL SWITCHES
  • COMPRESSOR / CONDENSER REPAIR - home
  • COMPRESSOR / CONDENSER INSTALLATION ERRORS
  • COMPRESSOR / CONDENSER LEVELING REQUIREMENTS
  • COMPRESSOR CONDENSER NOISES
  • COMPRESSOR MOTOR INSULATION
  • COMPRESSOR MOTOR REPLACEMENT
  • CONTACTOR RELAY DIAGNOSIS & REPAIR
  • CONTROL CIRCUIT BOARD, A/C
  • COPELAND ELECTRICAL HANDBOOK [PDF]
  • CRANKCASE HEATERS
  • ELECTRIC MOTOR DIAGNOSTIC GUIDE
  • HARD STARTING COMPRESSOR MOTORS
  • HEAT PUMP OUTDOOR UNIT DEFROST CYCLE
  • LONG-ON CYCLING AC COMPRESSOR
  • NOISES, COMPRESSOR CONDENSER
  • REFRIGERANT PRESSURE READINGS & CHARTS
  • SHORT CYCLING AC COMPRESSOR
  • TIGHT or SEIZED AC COMPRESSORS

Suggested citation for this web page

AIR CONDITIONER DIAGNOSTIC FAQs-4 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS

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