Photograph of  This new compressor was placed directly against
a brick wall. One third of its condenser coil cooling ability was blocked.Air Conditioner & Heat Pump Repair FAQs
Diagnose & Fix Air Conditioners & Heat Pumps Set#1

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Air Conditioning & Heat Pump FAQs

Questions & answers about fixing problems with air conditioners & heat pumps posted originally on the air conditioning & heat pump home page.

First set of A/C & heat pump questions & answers help diagnose and repair or adjust air conditioning & heat pump systems.

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Air Conditioning & Heat Pump Troubleshooting FAQs-1

Flex duct in a horrible routing of excess lengths (C) Daniel FriedmanThese 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 GUIDES A/C / 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 LIST

On 2013-03-21 by (mod) - Air conditioning is really quite interesting.

John Harlom said:

Air conditioning is really quite interesting. You have so many crazy photos. I cannot believe that some of those are real. I couldn't imagine having an air filter that dirty. Way gross. For me trying to figure out how an air conditioner works is better represented visually.

John we entered your comment without the link - as comments software does not permit insertion of links out.

Yes all of our photos are real;

We agree that sometimes a sketch is very helpful in understanding mechanical systems. For that reason we have included literally hundreds of sketches and diagrams here at InspectApedia, many of them provided courtesy of our associates and friends at Carson Dunlop Associates, a Toronto home inspection firm and education company.

On 2013-02-21 by sue tarranz

my markes cooler/ref no cooling although comprsor,condenser coil is clean.please help me

On 2013-02-17 by basam

the motor of AC in my room does not stop running all the time .is that right?

On 2013-01-05 by mike

goodman split system heat pump - pressures moderate and steady in cool cycle but rise gradually and shut down compressor within 5 minutes in heat cycle. Thoughts? Thanks.

My ac / heather unit will not start with out turning the breaker box off for a few sec"s Some one told me it might be the points on the unit and replace them ?

On 2012-12-24 by Anonymous

When unit is turned on outside fan comes on then a delay the compressor trys to start then goes off what up with that?

On 2012-10-19 by zoe - red compressor led light on the inside unit turns on

I turn my aircon on cooling option and within 5 minutes the red compressor led light on the inside unit turns on and it starts heating I've tried leaving it on to see if it cools back down again but it doesn't?

On 2012-10-17 by (mod) - ac fan not working and smoke is coming out with noise.


In cases such as you describe,

Watch out: Shut that system off immediately - There is serious risk of an electrical fire.

Turn off power, and if smoke continues, call the firemdepartment from a location outsidemthe home.

On 2012-10-14 by maria

ac fan not working and smoke is coming out with noise.

On 2012-10-03 by (mod) -

Something doesn't make sense to me; if the blower fan in the INSIDE AIR HANDLER is not running, I would not expect any significant airflow through the ductwork. Are we mixing up the indoor air handler fan and the outdoor compressor/condenser fan?

On 2012-10-03 by Darlene S

So I just tried turning the thermastat up and the fan cut off but there was still air comming from the vents for at least 25 minutes with no fan running.So I turned the themastat back down to make it cooler and the fan would NOT ocme on.So

I went to the breaker box fliped the braker off and back on nothing did this two more times and on the third time the fan came back on.Cool air comming out and all like it is suppose to.
I just worry about when the fan kicks off at desired temp.It may not come back on and the unit will burn up.
You can still hear a the unit "running" but no fan will be on.

On 2012-10-03 by Darlene S

My air conditioner works really well until the desired temperature is reached.
The fan turns off like it is suppose to but air still comes from the vents for a very long time afterwards and most times won't stop until I flip the breaker off.

There is no build up on the filter in the air exchange and no debris or shrubs around the unit itself.What would cause this?And is it safe to Not turn the breaker off and let it run (without the fan) or will this burn up the unit?
I know it will at least run my electric bill through the roof!
Thanks for any advice.

On 2012-09-16 by (mod) - air conditioning system has NO return air taken from inside the home


If you are saying that your air conditioning system has NO return air taken from inside the home, that's not a reasonable design - too costly to operate;

If you are saying that there is no air flow in to the return air inlet, then I suspect there is a dirty filter or a duct disconnection or leak problem to find an dfix.



On a 20 year old system I'd replace it.
On a newer A/C system in good condition but with a damaged coil that needed replacement, I'd consider that move.

What does your heating tech say?

On 2012-09-13 by Anonymous

A/C unit does not have intake suction from inside of home where filter is located.

On 2012-09-13 by debbie

Is is worth replacing coils on a/c or better to buy new unit?

On 2012-09-06 by (mod) - no air coming out of A/C supply registers

Ken as you have no air coming out of A/C supply registers it sounds as if the indoor air handler blower fan is not running, or if it is, that something (iced coil or dirty filter or crushed or disconnected ducts) are blocking air flow. I'd start at the top of this page and go through the diagnostic suggestiosn.

On 2012-09-06 by (mod) - to find work and to emigrate to another country as an AC technician

Sofene, to find work and to emigrate to another country you will need to look for a match between your skills and those that employers are seeking - I imagine there are job search websites on the internet that might be helpful to you and where you can post a resume. Not here, however - InspectAPedia is an online encyclopedia, not an employment service. We wish you the best of luck. Daniel

On 2012-09-05 by sofiene

hi im sofiene im 18 years old i live in tunisia and after school i want to move there and work please,thank you

On 2012-09-04 by Ken

The A/C unit is running outside but no cool air is blowing through the ducts. We put the thermostat temperature lower and nothing happened. If the thermostat is temp is put higher the the actual room temp, the A/C unit outside does stop. Also tried to run just the fan, but it did not work (does not start). Yesterday the A/C unit worked without the fan, after letting it off even with turning off the breakers for a ahile, it worked again through the night. This morning the blower stopped working again.

On 2012-09-02 by Steve H

Very informative info!

On 2012-08-29 by Yashu - Condensate Drip Tray and it was dry,

Yesterday I checked Condensate Drip Tray and it was dry, I noticed this as I checked before and when I am passing by some other houses I can see dripping water from the drip tray all the time. Is this any problem with the AC? I also checked for any clog but I am not seeing any water in the tray so wondering what could be the issue or it's normal!

On 2012-08-28 by (mod) - AC was getting weak. We shut it off over-night. In the mourning it was working.

Anon, what you refer to as the "condenser" that was swapped out was probably a start/run capacitor - an electrical component. Often a new capacitor can get an iffy electrical motor running again by giving it an extra electrical "kick" to get spinning. But if the motor is fundamentally failing, say by a bad internal bearing or some other problem, eventually even the new capacitor won't get it working. The bad motor will need repair or more likely, replacement.

At your outside A/C unit listen to hear what's happening - if you hear a humming there is a motor unable to start. When a fan won't start we suspect a bad start/run capacitor for that motor, or a bad fan motor or bearing itself.

I think the condensate drain problem is a separate issue.

On 2012-08-28 by Anonymous

AC was getting weak. We shut it off over-night. In the mourning it was working. Kept apt. with tech that we made the day it stopped. He sucked water out of the PVC were discharge water comes out from the AC. 3 weeks later, AC blowing warm air again.

Tech came, showed me the condenser(?) - (that small can about the size of a 6oz drink) was swollen. New condenser(?) installed & it worked again, for a week. Now it stopped blowing cold air again. All three times it rained heavy. Made sure the water from the unit can get out since I suspected rain water might be preventing the run-off water from the AC unit to get out.

Also sucked it with a shop vac. This time and previous, fan in the compressor (the lager unit outside) was not rotating. The first time it was shutting off & on in approximately 5 minute intervals. What's causing this? could wrong amperage (but I did not change anything) blow the condenser? Could water short-circuit the unit? If so, why did this not used to happen but is now? It ran fine during hurricane Irene.

On 2012-08-27 by Anonymous

my blower fan is good and the condenser but the fan will not run

On 2012-08-22 by Nicole

My AC unit is set on the ON mode at 65 degrees, outside temp is in the 100's,. Around 6 at night the AC starts blowing warm air. Also, temp reading on thrmostat never go's below 80's! Grandma can not survive this, what do I do?

On 2012-08-18 by Rick

The 30 amp circuit breaker keeps popping off. Where should I begin to look in order to diagnose the problem?

On 2012-08-18 by Shadow

QUESTION: Is that mean my A/C has something wrong?

My A/C works almost 24 hours, I need your suggestion. I am in Texas. I did measurement on my A/C 3 days ago.
In the late afternoon around 6:00pm to 8:00pm. Out side temperature is around 100 to 102 F. I set the thermostat on minimum around 55 to 60 F. It take the A/C unit a hour to get supply temperature around 68F and the zone temperature is 85F. But after one hour the supply temperature still kept at 68F and zone temperature is 85F.

The other reference is I turned my A/C on 24hours for three days, when I left I set it to 90F, When I back to home I set it to 85F ( I only stay at home about 9/24 hours.) I only use A/C and light(one 30W light, I use it around 3 hours for 3 days) no other electric consuming equipment. My electric meter give me 115 kWh for these three days.

On 2012-08-15 by Shads - My split ducted AC stopped blowing cold air

My split ducted AC stopped blowing cold air. I called in the serviceman and he had to replace the capacitor.

The AC blows cold air again but not as it used to be - it is weaker. We measured the air temperature coming out of the ducts and it reads now 66F whereby my other AC in the living room still reads 59F.

Serviceman stated that the AC compressor is aging and should eventually be replaced. I am a bit doubtful about that. Please advise what can be the problem?

On 2012-08-14 by Anonymous

air condition on no cool air.

On 2012-08-12 by Yvonne

Hi, I have a Maytag 18,000 BTU 220 Window Unit. Recently it had been shutting itself off, and now does not blow air at all. The compressor seems to turn on still, but there is no air flow at all from the fan. Is the unit shot? I've been told by an electrician that the unit is no good and I had to replace the air conditioner.

On 2012-08-10 by (mod) - condensation tray fills up with water and shuts air conditionor down


thank goodness for that - else a leak out of the clogged condensate tray or drain would perhaps flood the building and cause damage. Better find and fix the clogged drain.

On 2012-08-10 by Bob

condensation tray fills up with water and shuts air conditionor down

On 2012-07-30 by (mod) - the outside refrigerant high and low pressure lines seem to be backwards

Don, did you call the HVAC tech who installed your Goodman A/C compressor just a month ago? Surely the tech will want to return to check and fix the trouble.

On 2012-07-29 by Don

I just had a 900.00 compressor replacement on a goodman ac... about a month later, it quit cooling. Reading this i checked for ice and found the inside unit is about 20% iced over(iced on bottom part).

Before I found the ice, and before i turned the unit off I found that the outside lines seem to be backwards ( the larger pipe is hot and the smaller pipe is cold)the smaller pipe inside is cold too. Is this normal for an iced up unit? Is it posible they x-crossed the lines while installing the compressor? I turned the unit off and just have the fan alone blowing to let it defrost faster. Would like to see if I can get an answer to this before turning it back on and messing it up worse.

On 2012-07-29 by (mod) -


Yes indeed an animal shorting out electrical wiring terminals at a start/run capacitor can destroy the capacitor or other components.

On 2012-07-27 by (mod) - air is coming out of your vents but is not cool and the outside compressor/condenser is not running

K Shipman

If air is coming out of your vents but is not cool and the outside compressor/condenser is not running then at least we know the problem is probably there - or in a control or control board. If your compressor has been replaced and failed repeatedly something's wrong, perhaps an incomplete diagnosis, dirt in the system, or a diagnosis problem. Have a polite conversation with your HVAC service company's service manager and review the history and ask for a senior technician to help figure out what's wrong.


We don't know if the problem is in the outdoor condenser unit's compressor motor itself or something nicer like a bad start/run capacitor or relay or wire or control. It's worth asking for help from someone with experience and training.

On 2012-07-26 by KShipman

about half way through the day yesterday my house temp started climbing and when i look at my thermostat it said 81! i had it set at 73

. I go to look outside to see if my unit was working or the fan was turning, nothing! the air coming out of my vents is lukewarm at best. someone suggested it could be my contactor,

but i looked at it, no burned or rusty spots. we just had our compressor replaced in march. it had broken two times before that! so over this unit constantly breaking down, HELP!

On 2012-07-25 by PEdwards

My central air conditioner has been working fine...albeit often but now it's only blowing warm air. When I turn on the A/C and go to the outside unit, I hear a distinct difference about 10-15 seconds after the fan kicks on. The fan will continue to run but I don't hear what I believe to be the condenser. Your article suggests one of the root causes could be malfunctioning parts internal to the compressor. Could this be a DIY (testing and/or repair) considering I have very little experience in HVAC.

On 2012-07-22 by Viv

I found a fried lizard laying across what appears to be the terminals to a large capacitor. The AC will not kick on. Could this have shorted it? It is a RUUD unit.

On 2012-07-21 by qazi

my split is not showing any sign after voltage suddenly increases . is there any fuse problum or compressor damage ?

On 2012-07-21 by (mod) - cleaning even a small amount of dirt off of a squirrel cage blower fan makes a huge improvement in air flow.

I add to anon's suggestions that cleaning even a small amount of dirt off of a squirrel cage blower fan makes a huge improvement in air flow. Try that first, working meticulously.

Second, going to a pleated filter can give good filtration while, thanks to the larger surface area, much less restricts air flow.

On 2012-07-20 by Anonymous

@ Mike

I would look into replacing the filter with a more flow-efficient type that would increase the airflow and still provide proper air filtration ... It could be that you are using HEPA rated filters rather than standard filters, and if you dont need the HEPA rated filtration you could quite nicely do without it...

Aside from that option, replacing your fan or blower unit may prove feasible. It may be that your current fan or blower is dying on you or you just need a more powerful unit to blow air through thick air filters (especially if you are using HEPA filters and you need to keep them for health concerns...)

On 2012-07-20 by Mike - ran the system with no air filter

Just got done replacing my condenser fan motor and capacitor...finally I have cold air again.

Removed the filter from the inside unit as it was dirty but didn't have a new one, so let it run a few hours with no filter.

Two rooms in my house have always been 'hot' due to low airflow from the registers, but just dealt with it for many years. (I have tried both expensive, cheap, reusable filters - same result.)

I checked the airflow from these registers (with no filter in place) and there was GREAT airflow, and the rooms were both quite cool.

I bought new filters and installed one, then checked airflow in these rooms again.

As always, very poor airflow.

Since my electric bill was $400 this month (of course it's the hottest June in Colorado on record) I'd like to help with it's efficiency.

So, my AC has restricted airflow when the filter in place, and my AC is working harder than it needs to.

What, if anything, can I do to help this situation? I certainly can't go for long without a filter...any advise is appreciated.

On 2012-07-20 by (mod) - Standards for Air COnditioning System Cooling Capacity or capability required for rental units


On Standards for Air COnditioning System Cooling Capacity or capability required for rental units

There is no national code or standard for the cooling capacity nor turn-on date for air conditioning in rental units, though there may be state or local housing authority standards for cooling in your municipality - that's something for you to ask your local building department or rental housing authority.

Indeed if a cooling system is under-sized it is likely to be unable to keep up with cooling your rental unit in very hot weather. The actual ability of an air conditioner to cool an occupied space is of course affected by the properties of the building as well as the air conditioner. So picking an A/C unit's BTU cooling capacity, normally based on square feet alone, can get us in trouble if the particular building has lots of sun-exposed windows, or other reasons for high heat gain.

Certainly in our research to answer your questions we found some municipalities where there is a local rental unit housing authority to whom complaints should be addressed if a landlord refuses to respond to an air conditioning operating problem in a reasonable amount of time.

E.G. quoting from Montgomery County Maryland:

To file a complaint, please provide a brief description of the problem, the address where the violation is occurring, along with a specific location (if applicable). The caller's name and phone number are requested so that the inspector can call and provide an update of their findings or, if this is a rental property, to schedule an appointment.

On 2012-07-19 by Brent

My rental property management agency told me that my unit's AC capacity is only required to cool my townhouse (1800 sq ft) to 15 degrees below the outside temp. Is that correct? I don't believe them.


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