Frequently Asked Questions (and answers) about how to Buy, Diagnose, Repair Air Conditioners & Heat Pumps:

These questions about air conditioning and heat pump systems help diagnose problems with those systems such as lost cooling, noises, condensate leaks, or failure of the equipment to start or stop running.

We include links to air conditioner & heat pump inspection, installation, diagnosis & repair article series explains in detail the inspection, troubleshooting diagnosis, and repair of all types of residential and light commercial central air conditioning and heat pump systems.

This article series describes how to inspect and repair all types of residential air conditioning systems (A/C systems). Information for home buyers, owners, and home inspectors about A/C or heat pump system problems. Page top image provided courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].

Air Conditioning or Heat Pump System Questions & Answers

These Q&A about troubleshooting air conditioning & heat pump systems were posted originally

at DIAGNOSTIC GUIDE A/C or HEAT PUMP - be sure to check the guidance given there.

Snyder general melted wires in combustion box

Snyder general melted wires in combustion box On 2017-02-26 by mike

Reply by (mod) -

I don't know what to make of that comment

but

Watch out: if wires are melting in the control box for your heating or cooling equipment shut down the electrical circuit immediately as you risk a fire or shock.

If I lower my thermostat more than 1 degree at a time unit stops cooling and temperature goes up

I have a carrier heat pump. if I lower my thermostat more than 1 degree at a time unit stops cooling and temperature goes up On 2019-06-27 billy

On 2019-06-28 by (mod) -

We need to be specific about the difference between the two cases of lowering by one degree or lowering by more than one degree on your thermostat. Is it that the a compressor motor turns off and one case and not in the other?

Backup electric heat on pushes up COOLING costs

My daughter lives in a 3 year old apartment with two Heat Pumps mounted in the outside walls below her picture windows. One heat pump is in her small bedroom and the other one is in her living room/kitchen area and runs the most I believe.

Her electric bills the past two months have gone through the roof, I am wondering if one of the heat pumps might be the cause? If so, how might I diagnose the problem and determine which heat pump is the cause.

Details: It is mid-winter here in NJ but the temperatures have not been too bad, a mild winter, very little snow. During past winters, her electric bill has ranged around $30 to $50 max. per month. However, her last month's electric bill was $65 and her current electric bill jumped to $103! Her usage of her TV, lights, refrigerator and microwave remain constant and doesn't explain her much higher electric bills the last two months.

She keeps her Thermostats on each Heat Pump always set at 72 degrees. I just learned that heat pumps might have an electric back-up heater built into them that comes on when the outside temperatures drops too low for the main Heat Pump Function to operate well to give sufficient heat inside.

Might one of my daughter's heat pumps be malfunctioning resulting in higher usage of electricity and higher electric bills?

I can envision that if the main heat pump with its freon is not working or not working well, then the built-in back-up electric in the heat pump might be kicking in and doing all or most of the heating at a much higher cost .

Is my theory correct and if so, how might I diagnose the heat pump to verify the problem before calling and paying for a Heating and Cooling Repair Company or bothering the landlord to do the same? On 2019-02-27 by Gary

Reply by (mod) -

Thank you for an interesting question Gary.

What you can do is ask the heat pump or air conditioning service technician to measure the current draw at the compressor units to see if there's an abnormal behavior indicating that there's something wrong with the equipment.

I suspect that in cooling mode an improper control is turning on backup heat, or vice versa.

If your unit is running in heat mode and backup heat is on

In the above unit 1 1/2 ton when run in the heat mode the fan will never stop running, in the A/C mode fan starts and stops with the outdoor init On 2017-01-31 by Tom

Reply by (mod) -

Tom

If your unit is running in heat mode and backup heat is on, the backup heat and blower fan will run when the outdoor temperatures are so low that the outdoor compressor for the heat pump can no longer provide heat.

Heat Pump Backup heat strips are coming on even when the tstat is disconnected

I have a Goodman A24-10 that the heat strips are coming on even when the tstat is disconnected. I have replaced the sequencer and fan motor relay. The heat strips test as being good on a multimeter. Any idea what might be causing this? On 2017-01-05 by Mkhunter810

by (mod) - Goodman A24-10 that the heat strips are coming on even when the tstat is disconnected

For starters,

Disconnect the thermostat at the unit, not at the thermostat. That eliminates shorted TT wires.

Then I'd look for a failed relay or control board

Thermostat set to 73 but it feels like 62

inside temp is set at 73 thermostat shows 73 but it feels like 62 in here help, please On 2016-01-21 by Anonymous

by (mod) -

If the thermostat is being warmed by another source: heat output, sunlight, warm air currents in the wall, or if is defective we might see the condition you describe. After all the thermostat is only measuring the temperature at its own spot.

When I turn on the heat all it does it blows out cold air

I have a split unit that when I turn on the heat all it does it blows out cold air. I've check the thermostat and it does get 24v,the blower works,outside unit turns on and the fan is working. My question is what else could I check to try to fix the issue? On 2015-12-30 by Anno

by (mod) -

It sounds as if you need an HVAC service technician who will probably check

1. the reversing valve and other controls that switch from cooling to heating nmoder

2. the operation of your back-up heat for this heat pump system: if outdoor temperatures are low.

Question: squealing noise coming fron fan unit

have a standard heat and air unit that has started making a noise like a fan squealing. It comes and go. Is there something I can check or do before I call a service man.

(Jan 23, 2014) robert said:

I

Reply:

Anon, search InspectApedia for

HVAC Noise Descriptions & Recordings - Group 5

to read about this noise and its common causes.

Or take a look at AIR CONDITIONING & HEAT PUMP NOISES

You may have a failed fan bearing if you are indeed talking about the indoor blower unit; if the noise is outdoors I suspect a compressor problem.

 

Question: I changed the HVAC evaporator and refrigerant twice but the unit only cools for 24 hours then blows hot air.

have changed the evaporator and refrigerant thrice at a service workshop but the ac only cools for 24hrs and then blows hot air thereafter. what could be wrong?

(Feb 25, 2014) Anonymous said:

i

Reply:

Your system is leaking refrigerant

 

Question: my A/C is blowing hot air and the outside compressor is not working. Help me solve the problem

im getting 102 deg heat and should be 115. I changed sequensor and relay and fuse link (Mar 7, 2014) Anonymous

Reply:

Sure Daniel,

Click on the article titled

DIAGNOSTIC GUIDE A/C or HEAT PUMP

that's the best place to start.

 

Question: How do I decode an alarm fault on a humidifier

How do we daigonise the unit thats giving hummidifier alarm fault

(Apr 1, 2014) Ogunsan Ayoola said:

Reply:

Ogunsan
I think I'd start by picking up a copy of the installation and operating manual for the humidifier. Usually there is a table at the back that tells us for that *specific brand and model* humidifier just what sets off the alarm and if there are fault codes which code means which problem - that will steer you to the proper action.

 

Question: fuse blows when I switch to cooling mode

I have a problem with tempstar gas pack when I call for a/c it blows the 5 amp fuse on the transformer it does it on a/c only heat work fine any help will be great.

(May 6, 2014) gtucker said:

Reply:

GT, so if I've got it right, when you switch to cooling mode a fuse blows; what's different? Since the air handler is the same, one would suspect the compressor circuit, motor, compressor fan motor, or a control for the cooling components.

 

Question: system only runs ok on Heat

I have a Heil model number PH5036AKB4 ac/heat unit my problem is that it will run fine on heat no problems at all but on air it will blow cool air for about 30 mins if I'm lucky and then it just stops blowing

and then u have to cut it off and wait for it to want to work again which can take any where from a few hours to two or three days please help it's so hot and I have asthma what can I do to fix it Thanks so much (May 9, 2014) laurie

Reply:

I agree that you need an on-site visit from a trained HVAC tech.

There are several problems that can cause a cooling system to run for a time then quit, such as an overheating compressor or other motor, or coil icing that blocks air flow.

Something like a low refrigerant charge (find and fix the leak) or a defective refrigerant metering device could be at fault.

 

Question: loud thud when air conditioning fan comes on

My AC unit from time to time makes a loud thud like noise when the fan comes on and begins to run. The unit puts out cold air, so I am suspect the motor might be getting old and the bearings are drying up. The unit is about 11 years old.

(May 20, 2014) Mike said:

Reply:

Mike I'd look for loose fan mount bolts or a loose fan connection to motor shaft too.

Question: air conditioner runs but is not cooling off the house

Anonymous said:

AC not cooling, hooked up gauges and low side is in a vacuum. what is most probable cause for this?

5/28/14 linda said:

My air condition is running but it isn't cooling the house off.

Reply:

Please see the diagnostic advice at LOST COOLING CAPACITY and let me know if questions remain

Question: the dog ate my air conditioner wiring

Kevin Bresee

Hello,

I have a Rheem central air unit Model: UGDJ-05EAUER Serial: EB5D302F499606255. My dog months ago ate wires outside and blew the board, thermostat, and some fuses.

I had all fixed accept I just got a new thermostat and checked wiring and my problem is that the heater had worked but now that its hot the AC turns on all systems go but then it keeps shutting off and the new board is suppose to have a diagnostic light but tells me nothing.

Cold air comes out of registers, a little slower, I can see the blower motor spinning in unit/air handler and outside compressor is spinning and staying on even when the blower motor shuts off. I looked at the only capacitor inside where blower motor is and it is not swollen or anything but unable to check voltage.

Please help 98+ temps lately and cant afford service!

Reply:

Kevin I suspect that either not all of the damaged wires were fixed, or a short when the dog ate the wires damaged a control board or relay that you've not found.

Question: window air conditioner plugged into the wrong voltage, what do I do now?

I plugged my window air condoning 115 volt in 220 volt by mistake and I was not aware that the plug I have used was only only 220 volt I have in the house. the A/C went on then shut off by itself and It did not want to turn on again. the cable and the plug it is fine .

I checked the circuits brakes are fine too. What I should do now? thanks. Safwat (May 30, 2014) Anonymous

Reply:

I'm mystified about how it was possible to plug a 115V appliance into a 220V electrical outlet: the wall plug connectors are quite different.

But if someone managed to do so, possibly by splicing on a 220V plug, the voltage could have damaged a control or circuit board in the device.

Check for an internal fuse blown in the AC unit. - Moderator

(June 6, 2014) Softwat

Probably overseas; plug adapters that only convert plug shape are common since most electronics' power supplies can accept 240v.

Reply from moderator:

No, Softwat, air conditioners do not use low-voltage power supplies such as the type you describe, and a system designed to run on 120V is not likely to enjoy being wired at double voltage.

Question: air handler keeps stopping

(June 6, 2014) Anonymous said:

inside air handler runs then shuts down for two to five seconds then starts again. this happens two to three times a cooling cycle. is there a problem?

Reply:

Anon this sounds like a control board or relay problem. I'd give your local AC repairman a call to get some diagnostic help. Short on-off cycling can cause further damage on some systems.

Question: compressor motor won't start

(June 8, 2014) Anonymous said:

Fan is running but compressor does't start

Reply:

Take a look at these diagnostic procedures to figure out why your AC unit won't run

DIAGNOSTIC GUIDE A/C or HEAT PUMP

HARD STARTING COMPRESSOR MOTORS

Question: shut off the wall switch to a Rheem Criterion II furnace - which shut off the fan.

(June 9, 2014) xenaon

i rent from a bad guy. He shut off the wall switch to a Rheem Criterion II furnace - which shut off the fan.

Before, if I turned on the wall switch - the fan went on if the AC was on. Now, it doesn't. Inside my apt the AC (2) and Furnace (f) breakers are fine. 3 hours later, the bully shut off the gas water tank downstairs - turning the red valve switch on the pipe to horizontal, then setting the control to off and "vacation" so the pilot light is no longer lit.

On the roof, there are 12 SEER 10 AC units for the central air for each unit.

The small white compartment box is open and it says UP/DOWN - that you can take the cartridge out to shut the AC unit off. Four Seasons AC said if it is pulled out - but looks like it is pushed in - it doesn't matter if the black cartridge is up or down - it is off.

BUT: they said the heat to the Rheem and the furnace fan should still go on even if the roof AC was off. The heat and the fan on the Rheem do not go on.

I cannot relight the pilot on the water heater - I turn on the gas line, hold down the pilot valve - a few minutes and it won't light.

I cannot find a way to turn on the Rheem Criterion II gas/AC unit. What else needs to be turned on? Thermostat (Honeywell) does not ignite the AC or fan or heat - but it could not possibly be the thermostat as the person who shut off the fan switch - also turned off the water heater.

Can anyone tell me how to get back on the furnace/AC in the closet - and did the bully per chance just take out the cartridge to the AC on the roof without worry of electric shock? If it is not pushed in - do people feel it is safe to just push it back in?

Four Seasons AC/Furnace said the AC circuit breakers are connected to the roof AC - and the furnace circuit breaker is connected to the closer furnace/AC.

Reply:

CHeck that the equipment's power switches are ON including at the electrical panel, at the air handler (service switch), at the compressor/condenser (service switch).

Also check that the inspection doors to the air handler are closed securely and that there is no condensate pan flooded with water and thus tripping a condensate overflow pan switch.

Search InspectApedia for AIR CONDITIONER WON'T RUN for details.

Question: overheating AC compressor, won't start

(june 11, 2014) kuldip kumar shrivas said:

I am facing a problum of overheating of outdoor compressor , status is his fan and gas is proper and also his capacitor compressor is showing ok but after some time compressor is not working only fan is running , it may be overheating. How can i solve it.

Reply:

Kuldip, if supply voltage is normal then the compressor may be failing. You can try a hard start capacitor.

Question: Air conditioner won't work

(June 11, 2014) Anne said:

My a.c won't work,we've replaced the thermastat and it still won't work.the heat comes on but not the a.c nor the ventalation fan.
What do you think the problem might be?

Question: rhythmic thumping noise at the air conditioner / furnace

(June 13, 2014) Scottie

I have a problem with my Central Air Unit and Furnace. Turned on Air this year and there seems to be a rythmic thumping noise you can hear from the AC line to the furnace.

You can feel it in the cold air (coolant) line to the furnace. What is this from? Air in the line? Does it need more coolant?

Any help is great

Reply:

Scottie I'd like to help but just can't make a useful guess from must your note.

However take a look at our diagnostic article on types of air conditioning system noises to see if that points you in the right direction. See

inspectapedia.com/noise_diagnosis/HVAC_Noise_Diagnosis.php

 

Question: Frozen coils on the air conditioner, air blows but not cool

6/22/2014 Mimi said:

My parents called me and said that the air conditioner was not working. I went over and check out unit outside and the coils were frozen.

I turned off the unit and I tried to trouble shoot to see we can get it going again. It said that I needed to clean the coils and get the dirt out, change the air filter if needed.

I did all that but then a couple of hours went by and it still wasn't cooling down the house.

The air was blowing fine but it was not very cool air.

So then I went into the garage and check out the coils inside and they were frozen too. I then went and shut off the unit and waited until the next day when everything was thawed out. I looked to see if the wiring was somehow damaged too and it wasn't.

I started it back up again and I will go back to see if it has cooled down. I'm thinking that it might need a charge of gas what do you think?

Can you please give me some advice, if we had the money for a service call I would have already called someone 2 days ago. Im worried because my parents are elderly and it's been getting pretty hot.Please help with some adive

Reply:

Mimi,

the refrigerant gas in an air conditioning system does not normally need to be changed. Instead, let's diagnose the cause of coil icing such as a dirty air filter or a refrigerant leak.

See this diagnostic article on causes of coil icing and keep me posted

inspectapedia.com/aircond/Cooling_Coil_Frost_Ice.php

Question: Air conditioner has frozen coils

(June 22, 2014) Mimi said:
My parents called me and said that the air conditioner was not working. I went over and check out unit outside and the coils were frozen

.

I turned off the unit and I tried to trouble shoot to see we can get it going again. It said that I needed to clean the coils and get the dirt out, change the air filter if needed. I did all that but then a couple of hours went by and it still wasn't cooling down the house. The air was blowing fine but it was not very cool air.

So then I went into the garage and check out the coils inside and they were frozen too. I then went and shut off the unit and waited until the next day when everything was thawed out. I looked to see if the wiring was somehow damaged too and it wasn't.

I started it back up again and I will go back to see if it has cooled down. I'm thinking that it might need a charge of gas what do you think?

Can you please give me some advice, if we had the money for a service call I would have already called someone 2 days ago. Im worried because my parents are elderly and it's been getting pretty hot.Please help with some adive

Reply:

Mimi,

the refrigerant gas in an air conditioning system does not normally need to be changed. Instead, let's diagnose the cause of coil icing such as a dirty air filter or a refrigerant leak.

See this diagnostic article on causes of coil icing and keep me posted

inspectapedia.com/aircond/ACCoilFrost.htm

Question: air handler blows hot air

(June 24, 2014) Anonymous said:
Air handler started blowing hot air while in AC mode. temp was set to 77 OAT was 76 but very humid, turned unit off and waited until morning. Turned unit on and it was blowing cold air again. Unit worked for rest of weekend.

Call a service tech, everything checked out ok except for low refrigerant and superheat/supercool spread was a little off.

Unit again started blowing hot air last night at 11pm, again a very hot humid day. Is this a compressor starting to fail?

Reply:

Anon,

"... except for low refrigerant" is not "OK" - it means there is a refrigerant leak that needs to be found and fixed. AC units do not "consume" refrigerant.

Question: air handler won't turn off

(June 25, 2014) Travis Moragn said:
My air handler fan and heat strip want turn off

Reply:

Travis it sounds as if your system is stuck in HEAT mode. TUrn the thermostat down to below room temperature. If the system keeps runnning, turn everything off, wait 15 minutes, then turn it back on. At that point if the problem persists it's time to call a repair person.

Question: screeching compressor, getting hot

(June 28, 2014) Tim Williams said:
My a/c unit will kick on, the fan runs, it seems to cycle, but after the fan shuts off it sounds like the compressor will kick back on ( the fan won't) and it starts screeching, and getting hot- any suggestions.

Reply:

Tim, about that screeching air conditioner compressor unit, please see the diagnostic suggestions at

inspectapedia.com/noise_diagnosis/HVAC_Noise_Descriptions_5.php#Squeal

Question: no resistance across contactor coil

I am measuring only 1 ohm across my contactor coil. has the coil shorted which keeps blowing my thermostat fuse? some site said that it's the contactor

Reply:

Anon with 1-ohm:

You are measuring essentially no resistance - as if there is a short.

(June 29, 2014) Anonymous said:
Valerie Lg inverter system just stopped power still there says C6 or O6 in window will not come back on even manually.

Question: AC running for hours at a time

(June 29, 2014) Anonymous said:
my a/c is cooling. but it is running 1 to 2 hours at a time. how can I fix that run time

Reply:

Anon that operation may be normal depending on the thermostat set point, outdoor temperature, and building heat gain.

If you think the system has lost cooling capacity see LOST COOLING CAPACITY in the links further below Continue reading you will find

an ARTICLE INDEX to see diagnostic procedures

 

Question: determine the BTUh capacity of a York Air Conditioner

(July 1, 2014) Cindy said:
I have a york brand central air unit , and would like to know how many btu's it has

Reply:

Cindy see these HVAC data tag decoding guides

inspectapedia.com/aircond/Data-Tag-Decoder-Air-Conditioner-Heat-Pump.php

For York- Borg Warner air conditioners take a look at the outdoor compressor/condenser unit's data tag (don't wipe it or you'll wipe off the lettering).

The encoding of cooling capacity varies by equipment type and year.

On some the first two digits of the model number are MBTUs, so for example if you see

DWR 20 XXXX that's a 20,000 BTUH unit (two tons) of cooling capacity

Other model numbers encode the cooling capacity in the 6th and 7th positions, EG:
H1CB012506 - is a 12,000 btuh unit.

For models with this format

D-95A 30 N 080 06-A

The BTUH is in the position after the N - our example shows 080 or 80,000 BTUH

See Carson Dunlop Associates' Technical Reference Guide (cited in these articles) for full details.

(July 1, 2014)

cindy said:

my model is gva027 and serial number is efds166414, could you tell me how many btu's it is?

Reply:

Looks like this is a heat pump (the "E")
16,000 BTUH (using the 5th & 6th digits)

Check the owners' manual that should also give you a proper decoding key for your unit. Let me know if your manual says something different.

Question: bad Air Conditioner contactor relay

(July 1, 2014) Robert Wheeler said:

I replaced the contactor, the capacitor, the time delay relay inside the AC unit and the furnace 24V transformer which blew out because I didn't turn off the furnace switch at the breaker before changing the contactor and capacitor.

I even by-pass the thermostat by connecting the red and green wires to see if it would come on, which would tell me if my thermostat was bad or not. After all that it still only comes on when I press and hold down the contactor.

Reply:

Robert, did you connect the thermostat wires at the thermostat or at the other end, at the AC control?

Did you check for obvious burn or overheat marks on components like relays or circuit boards?

(July 5, 2014) Robert Wheeler said:

Hi Dan - Thanks for replying....I connected the wires at the thermostat. Also, today I replaced the circuit board with a new one and I still am not getting the AC to run without holding down the contactor.

(July 5, 2014) Robert Wheeler

It was the furnace circuit board that I replaced today. I replaced it thinking it may have gone bad after I accidentally blew the 24V transformer that connects to it.

Reply:

Robert,

Thanks for the follow-up. Your diagnosis and repair will certainly assist others.

I'll keep the remarks and at future edit move them into an appropriate permanent spot.

Connecting the wires at the thermostat is simulating a thermostat calling for the equipment to run but doesn't rule out a short elsewhere between those wires.

Question: How can I figure out if I need to replace my AC unit

(July 7, 2014) jkwinans said:

How can I figure out if I need to replace my AC unit on my camping trailer or if it is only a thermostat issue? Often when I get to the camper the air starts immediately, but when it reaches temperature it will not restart. This week-end it ran perfectly until I was almost ready to leave..... now it does not re-start again!!! Is it possible for an old lady to diagnose this or do I need a repair person?

(July 7, 2014) jkwinans said:

I should also add that neither the fan or heat will kick in either at least by using the control panel on the Coleman thermostat.

Reply:

JK

This is pretty easy. Just go to the end of the thermostat wires where they appear AT THE COOLING UNIT controller.

There if you jump the two thermostat connections, that's exactly the same as if the thermostat had called for cooling.

If the system responds normally then the problem is indeed in the thermostat or in the thermostat wires.

(July 7, 2014) jkwinans said:
Thanks for your advice. Since the cooling unit is on the roof I will need to wait until I can get someone to climb up there. LOL do you guys hire out?

Seriously, I appreciate your help.

Reply:

(July 8, 2014) (mod) said:
Keep us posted JK. And no, seriously we don't hire out - it would be a conflict of interest with that of InspectApedia's role in providing information not connected to other business activities.

 

Question: Goodman unit heating and cooling at same time

(July 14, 2014) Anonymous said:
goodman m#ARUF024-00A-1A cooling on but heating coiling are on at same time whats wrong

Reply:

Anon

Usually when aux heat won't turn off it's a control or control board or relay problem.

Question: humming compressor condenser unit

(July 20, 2014) Steve said:
The fan is not turning on outside just humming

My outside air is just humming when calling for cooling

Reply:

Steve, shut the system off and call a service tech. Could be a bad start capacitor or a frozen motor.

 

Question: used R22 heat pump

(July 20, 2014) Larry said:
I purchased a slightly used 2.5 ton R-22 heat pump to replace my 10 yr old a/c condenser unit. The "new" unit is pressurized but I don't know if the R-22 was pumped down into the condenser or was reclaimed and filled with inert gas.

Is there a way to determine without losing the R-22? Would a non operating condenser filled with some amount of R-22 show about 120 psi at 78 degrees F? I have tried locating the original installer but have had no success. Worst case, I will recycle whatever is in it and refill with virgin R-22.

Reply:

Larry, for an unknown charge that may be air contaminated most likely the system needs to be evacuated then recharged.

 

Question: sparks at the compressor unit

I bumped into the outside compressor and saw sparks fly, but the motor continued to run so I thought no more about it other than planning to inspect inside the unit for a loose wire.

The AC was no longer cooling however and I took off the door and found that a screw (probably from an earlier repair) had rolled over onto one of the connectors on the run capacitor.

The capacitor looked like it had been in a fire (smokey).

The compressor fan will no longer run. I assume the capacitor needs replacing. My question though is, how did the fan (not the compressor) continue to run just after the sparks flew, but will not run now?

JDStevens

Sorry! Forgot to mention the compressor no longer works also. Also assume that when the capacitor problem is fixed, both problems will be fixed. (July 27, 2014) Anonymous

Reply:

Anon,

You are right to turn off the system and replace the capacitor.

Possibly the capacitor that was fried by the loose screw short circuit is a start cap for the compressor or for both compressor and fan, but if the fan was already spinning it would continue to run until its next off cycle, then wouldn't restart.

Check too for a blown local fuse.

Question: starting and running capacitors on HVAC systems

At first, I thought the "fried" cap was the start cap, but its specs boast only 5 MFD and is oval shaped.

The other cap is cylindrical and its label has 80 MFD which has to be the start cap? It's a little confusing as I thought the run cap would have to remain closed to complete the circuit ..

perhaps it did until as you indicated, on the next cycle it wouldn't close again. Yes, the fan was spinning when the short circuit occurred.

I will probably replace both caps since they aren't very expensive. Currently, I have all power going to the unit turned off. I tried all day to find the capacitors, but no one that sells them is open on Sunday.

Home Depot, Lowe's, Ace, TrueValue don't stock them.

I checked the unit and its schematic for a local fuse, but found none and no mention on the schematic. (July 27, 2014) Anonymous

Question: Why are the control circuits of heating and air conditioning equipment 24 vac?

(July 29, 2014) Anonymous said:
Why are the control circuits of heating and air conditioning equipment 24 vac?

Reply:

Anon,

generally low voltage wiring and controls on HVAV systems are safer, more economical, and easier to install than using 120V simply to turn equipment on and off.

Question: freezing air conditioner

(July 29, 2014) margaret said:
the air conditioner freezes up on the inside and out side it will not blow any cold air

Reply:

Margaret, in More Reading links above see FROST BUILDUP ON AIR CONDITIONER COILS for an explanation and repair advice.

Question: fan won't turn off

(July 30, 2014) Anonymous said:
Fan on inside unit will not shut down after temp is reached and will not let condensing unit outside restart when needed.ruled out thermostat by swapping first and second floor units.

Reply:

Anon

The Indoor fan won't itself cause the outdoor compressor/condenser to start or not start, though a control circuit board or relay could affect both units.

Diagnostics for a blower fan that won't stop running are found at

inspectapedia.com/heat/Furnace_Fan_Wont_Stop.php

Question: compressure just buzzes

Aug 11, 2014) Anonymous said:
Helllo,
The thermostat kicks on the fan but the A/C unit outside does not turn on and just gives off a buzzing noise, is it a bad motor?

Reply:

xAnon, the problem could be a bad motor, relay, start capacitor or something else I've not thought-of.

Question: is my air conditioner sized correctly?

(Aug 12, 2014) Lou said:
I have a 1,200 sq ft apt 2nd floor - they just replaced both the outside and inside units.
They said it was a 2 and 1/2 ton a/c unit.
Is this the correct size for my unit?

Reply:

Anon,

You'll want to check out the BTU chart found in ARTICLE INDEX - titled BTU CHART for AIR CONDITIONERS / HEAT PUMPS

 

 

Question: who purchased & installed my heat pump?

(Aug 19, 2014) Miles C. said:
I bought a home and during the purchase the heat pump was replaced with a new AC unit
HUD says if it had done the repair I would find paperwork

How can I back track the unit to see who bought it? (Installed it)
The heat pump already installed could have been repaired
Now before winter I need to replace this new AC unit with a heat pump

Reply:

Miles

It sounds as if someone took a shortcut (cheaper to install air conditioner than a heat pump) or was just mistaken.

Your AC compressor unit will include a data tag with brand, model and serial number.

Most likely there are not so many installers in your area that you couldn't just give them a call to ask who installed the unit at your address. Start by asking each company if they install the brand you have. If they do, then ask if they installed yours.

Also, if an installation and operating manual was left behind (as it should have been) there may be a note with it on the installation date.

Keep us posted.

aircon maintenance

Tips to maintain your own air condition in home and in office.

There are things you must know on how to maintain air condition without the need of technician. Simple steps to fix it and if there is a major problem then you need to hire aircon services

 

Question: weird air conditioner noise

(Aug 30, 2014) Anonymous said:
A snowflake appears in the upper left hand corner of the thermosat and the ac unit doesn't work

(Sept 3, 2014) dan said:
I have a new unit 3 ton ac ,,the evap and cond was replaced ,,new line set ,duct was replaced ,I get 70 psi on low side and 200-210 on high side ,temp coming out of duct is 74-76 and return is 79-80,furnace seems to be blowning a lot of air ,

I took side cover of coil off and lower to mid is temp of 56 but mid to upper coil is 72 degree,,the outside fan has 114 degree air coming out of it ,,the low pressure line on out side unit seems to be 88 degree

(Sept 11, 2014) Carol said:

Our AC system is making an odd noise. It is coming from just behind where the filter sits, it is a loud, continuous, rhythmic like sound. The sounds is like a cross between a knocking and a drip. I left the house at 10:30 am and it was not making that sound. Both thermostats (up and down) stairs were set to off when I left. When I cam home at 3:30pm it was making that noise and it has not stopped. What in the world is it?

Reply:

I'm not sure Carol. I'd start by shutting off the system and removing the filter to have a look inside the return duct and plenum.

See NOISE AIR CONDITIONER / HEAT PUMP

 

Question: A/C heat pump switches off when it gets cold

Anonymous said:
My machine is not starting up. It switches off when it gets cold. Today it wouldn't start at all. What could be possibly wrong?

Reply:

Sounds as if your backup heat is not working.

Question: cold air does not shut off in winter

(Jan 22, 2015) Rachel said:
In winter time keeps blowing COLD air. The board to model UPNJ037JA2 has been replaced and still blowing very cold air.

Reply:

Rachel

If your thermostat is set to HEAT mode and the room temperature is below the thermostat set temperature then I suspect your system has a control or wiring problem and is not switching to heating mode or equally possible it switches to heating mode but low outdoor temperatures are calling for use of your backup heat source and that's what is not working.

As you replaced a control board someone also suspected a control problem.

A check of voltages on output control circuits from the control board can tell you if that component is calling for heat. Proceed from there to check the backup heating system components .

 

Question: Eurospace EPAC 12E not working

Help..when I press the power button on my europace epac 12E portable ac it make loud noise...and the loud noise goes on n off. I think it is from the compressed. Help anyone..what can I do?

(Feb 5, 2015) han said:

Reply:

Han

I would leave the system turned off for safety. If the compressor is seized or seizing and you keep trying to start it more damage may ensue. A service call may detect something less costly (if we're lucky) such as a failed start capacitor. It's time to call a service tech.

 

 

Question: problems with condensate drain & bare wires on condensate sensor switch

my goodman 3 ton ac unit had a full drain pan tonight. I drained the pan with my shop vac then cleaned the condensate pipe with my shop vac, vinegar solution and a bit of internal scrubbing. All is dry and looking good now.....

EXCEPT!

a few inches 10? behind what I assume is the automatic shutoff trigger attached to the drain pan that makes the ac unit stop (but not the blower) - behind this shutoff, I see two exposed wires!!! a red and a black...

with copper ends (little thread looking copper not the thick single wire type) sitting in the drain pan! Is this OK?

Do I need to some how crawl back there and find out what they were supposed to be attached to, or are they part of the auto-shutoff mechanism and I don't need to panic?!?! Thanks for your help!
daniel@laustintranslation.com Daniel (

Reply:

No panic, Dan but indeed it sounds as if there is a defective shut-off switch in the drain pan. I'd have it replaced. And watch to be sure that drain is not clogged.

 

Question: water on floor when A/C is running

I am getting water on my floor when the A/C is running. The A/C works fine. Can it be repaired?

(May 16, 2015) Mike said:

Reply:

Yes it can be repaired.

Look for a leak in the condensate handling system

Search inspectApedia.com for

Air Conditioning Condensate

to see the diagnostic procedures you'll need.

 

Question: compressor won't turn off

Compressor wont shut down after unit is turned off. (May 16, 2015) Ron said:

Reply:

Your HVAC tech will probably start by checking for a failed relay or control board.

Search inspectApedia.com for

Air conditioning compressor diagnosis

to see the diagnostic procedures that will help you understand what is probably happening.

 

Question: A/C Repairman says Federal Law Rerquires Thermostats to be set at 76 degrees F

11 Juyly 2015 (6 days ago) Whitey said:
My AC servicer tells me that federal regs require me to keep my AC thermostat set at 76. I have kept it at 72 since buying the unit. Why the sudden change?

Reply: Baloney!

Whitey

I have not found any U.S. Federal regulation that tells a private homeowner what thermostat settings are required. In my opinion, BALDERSASH!

There are federal guidelines for the workplace: in the workplace the minimum temperature for indoor workplaces is 68 degrees F, maximum is 76 degrees F.

The acceptable range for indoor humidity is between 20 and 60 percent. Source: U.S. DOL & OSHA & ASHRAE 1975.

Question: A/C external static pressure readings & standards

Tom said:
I have an older technician says Goodman air conditioner and label is unreadable. Numbers given by technician MLE25-1 890501092. I need to located the model number for unit. These numbers do not register with Goodman in their database. Label is on unit but weathered.any assistance on how th locate other numbers around unit internally etc. to get model number? On coil or in frame work? thanks Tom.

16 July 2015 Filters and A/C external Static Pressure said:

I have A/C Fan with 2.5” wg Static pressure and have two filters to put in the way MERV 16 and prefilter. the duct to the area is no longer than 15 ft. Is that Static pressure enough to have these two filters in the way.
Thank you

Reply:

Filters:

According to Brendon Reid's nice article on this

If you are really quoting a properly-made HVAC duct system static pressure measurement in inches of water column " wc then your number is a bit shocking. Most residential blowers won't create more than 0.9" wc. Your number sounds high, wrong, and likely to mean that the system is noisy and also return-air starved.

Typically we want to see 0.5 wc static pressure as a general rule of thumb. - see www.achrnews.com/articles/103710-interpreting-duct-static-pressure

- Brendan Reid is President of the Comfort Institute (CI), Bellingham, Wash. CI provides building science training and instruments for whole-house and air-distribution diagnostics and repair

He can be reached at 360-420-5049

For photographs of these various air conditioning and heat pump parts, and for an explanation of where these air conditioning components are physically located,

see A/C or HEAT PUMP COMPONENTS which discusses and helps you name and recognize various  Indoor A/C Components and Outdoor A/C Components

...

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

Or see these

Recommended Articles

• AIR CONDITIONING & HEAT PUMP SYSTEMS - home
• AIR HANDLER / BLOWER UNITS - home
• COMPRESSOR / CONDENSER REPAIR - home
• DIAGNOSTIC GUIDE A/C or HEAT PUMP - home

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

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