InspectAPedia®   -   Search InspectApedia

Photograph of an old burned-out air conditioning compressor unit AC / Heat Pump Compressor Diagnostic FAQs

HVAC compressor / condenser diagnostic questions & answers or FAQs:

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

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Diagnostic Q&A - HVAC Compressors & Condenser Units

AC Compressor © D Friedman at InspectApedia.com These questions and answers about troubleshooting and fixing air conditioner or heat pump compressor/condenser units were posted originally

at COMPRESSOR / CONDENSER DIAGNOSTICS - be sure to check out the diagnostic suggestions on that page.

[Click to enlarge any image]

Question: no air is coming out of our supply registers

I have a Coleman unit. Had heating probs 2 years ago leading to complete computer panel replaced, evaporator coils cleaner, gas regulator replaced. Two days ago, my A/C decided to stop working. I hear the freon flowing into the coil region, the fan outside is turning, but no air is coming out of registers. What can it be? - Cheryl 9/9/11

Reply:

Cheryl if you have no air coming out of supply registers the blower fan is not working or the duct system has become disconnected or blocked. Coil ice-over in the air handler can also block airflow. Start by determining that the blower is running and that the air filter is clean.

Question: water at the air return vent

what makes the water from an airconditioner build up in the return vent? - Connie Woyan 9/15/11

Reply:

Connie: if you see water at the return vent it may be condensation on a cool surface, or it could be condensate leaking down into the return vent from your air handler. You'll need to make a closer inspection of the air handler (blower unit) itself.

Question: what type of copper is used in HVAC refrigeration piping or tubing?

What is the content of copper tubes used in AC? (i.e I would like to know the contents of pipe which is being connected between the Fan and compressor of split AC) - Pratik Shah 10/1/11

Reply:

Pratik

Copper tubing used in A/C systems for refrigerant piping is just that. Soft flexible copper piping. While the differences between K, L, M and DWV copper piping are primarily in wall thickness, the the copper tubing alloy class may also vary for flexible copper tubing used in HVAC applications such as refrigerant piping and oil line piping.

1/2" K copper tubing has a wall thickness of about 0.049"

1/2" L copper tubing has a wall thickness of about 0.040"

1/2" M copper tubing has a wall thickness of about 0.028"

1 1/4" copper DWV piping has a wall thickness about the same as L copper or about 0.040"

The flexibility of copper tubing also depends on how it was produced: annealed vs drawn. Annealed copper is softer, suitable for flared and compression fittings, though it can also be soldered with proper edge smoothing/rounding.

Drawn copper is generally used for soldered fittings though drawn copper types A and B tubing can be joined with some types of compression fittings as well.

Details about the alloy mix of various copper piping materials is given by standard ASTM B88 and are providedin exhausting detail by copper dot org.

Question: no sweat on the suction line

what could be the problem when the sunction line of an air conditioner is not sweating? - Diana 2/3/12

Reply:

It may not be a problem - you'd need to describe the operating conditions in more detail. For example a cold suction line in low-humidity air may not collect much visible condensate.

Question: hard starting compressor

jon- ac system is less than a year old, when I turned on ac to check, condensor comes on then shuts back off, then 30-45 seconds after comes on again for 2-5 seconds. Whats wrong? - Jon Anon 8/18/12

Compressor on Lennox centeal air not turning even if the thermostat is activated.. It is blowing warm air.
Possible problem - Roger 7/8/12

Reply:

Anon: regarding your hard-starting compressor/condenser unit: we can't with confidence say what's wrong with so little information - your service tech can diagnose the problem, probably fairly quickly.

But a common cause of the symptoms you describe is a bad start/run capacitor or worse, a failing compressor motor.

Todd said to Roger:

Rpger...not a professional myself but I had the same issue. The motor on my outside unit had worn out to the point that it needed to be replaced. Forturantely for me it was under warranty from a unit that I purchase 4-5 years ago. This might be strange for most units but we've had some above average summers here in Texas the last couple of years.

Another thing my HVAC tech does is check and replace the capacitor if necessary. I've been told that if the capacitor is shot, it will expand, almost resembling a coke can that is about to explode. Good luck.

Thanks Todd.

Roger, presuming you checked tonassure the unit has power and the thermostat is calling for cooling, if the suggestions in this article didn't get your system diagnosed check the LOST COOLING article linked above at the ARTICLE INDEX the bottom of this article - Editor

 

Question: does it help to spray the compressor/condenser coils when it's hot outside?

Does it help to spray water on the compressor coils when the outside air temp. is 100+? The inside air is going up in the afternoon to 82. - Greg Warner 7/7/12

Reply:

Some readers have reported that their compressor was overheating and ran ok when water cooled - this is perhaps a diagnostic step but not a reasonable repair. And don't soak electrical components.

Question: oil in the capillary tube? - recurrent cap tube clogging

i have replaced my compressor from company and when i started it was giving cool air but the copper pipe out side (large) was not cool enough and after 40 mints its timer light flashes and after 10 more mints its down automatically. it happens again and again i sent back it to company technician is looking into it.

He said oil was in capillary and it needs flushing so he will replace its capilary since after cleaning its not fixed. do u think there is no fault in compressor? or what possibly is the problem.. - Wagar 7/11/12

Reply:

You'll want to check the installation manual to find the control light decoding for your brand and model of cooling equipment. Could be a control or control board problem too. It's just about impossible to flush a cap tube so replacement is normal.

But if there is debris in the system, or excessive oil, the new cap can clog as well; good practice would be to empty the system, pull a vacuum, flush the whole system, install a filter dryer, replace the cap tube, and recharge.

Question: A/C not cooling, condenser fan not running

Several days ago I noticed that even though my air handeler was rinning the AC was not cooling, I foudn that the condensor was not turning, I flipped the breaker (that apprered to be in the on position) and it worked for awhile.

15 minutes later I noticed that the condenser was not operating again so I flipped the breaker again it corrected the problem. I then went on the replace the breaker which seemed to correct the problem, the AC worked normally for several days.

Now I find the condenser is not working again and flipping the breaker fails the correct the problem. When the condenser was working it was providing good normal cool air.

The system is 2 years old. I assume I have an electrical problem in the condenser. What is likely to cause this problem and how can I test for it (I have a test meter) but I want to be careful because I know that a coil can retain a dangerous electrical charge even when all power is off and disconnected. - Rick 7/13/12

Reply:

typically we see if the fan spins, if it has power, and if the controls and fan contactor are bringing power to the fan when the condenser unit starts up.

Reader Followup

My problem turned out to be a bad contacter (damaged by ants) - Rick 7/13/12

Question: loud cricket chirping sounds at the compressor/condenser unit, and slow starting

outside unit making loud cricket sounding noise when running. Takes long time to come on when temp set low. - JT 7/276/12

Reply:

JT our link at the ARTICLE INDEX the bottom of this article NOISE AIR CONDITIONER / HEAT PUMP provides noise diagnostics.

About taking a long time for the A/C to "come on" when the temperature is set low: the thermostat is operating like an "on-off" switch that turns the air conditioner system on and off in response to room temperature.

It's not an accelerator.

So if there is an operating problem related to the system controls, the number of degrees below the room temperature to which the thermostat is set should make no difference in how long it takes the A/C system to start. As long as the SET temperature is lower than the room temperature the cooling system will turn on.

Question: cheating on a test?

(Mar 19, 2014) Anonymous said:

I want to know the difference between inverters and todays airconditioner. what are the comm on defects of inverters and what refrigerant is use

Reply:

Anonymous, those are fair questions but it sound to me as if you are in the midst of taking an exam.

Good luck on your test.

Question: Split AC system cools OK at night but not in afternoons

(May 24, 2014) Knight said:

Any body tell me what is the problem with my split ac It gives perfect cooling in night and morning but in afternoon its compressor turn on and off every after 15 minutes it can not give cooling from 2PM TO 6PM..

I checked gas, capacitor and connection and voltage its ok but i dont know whats the problem if you have any idea plz share with me

Reply:

Knight, as afternoon is the time the system works hardest I suspect the compressor motor is shutting down on thermal overload. If cooling it off with a water spray (DO NOT spray electrical components) that's likely to be the problem.

 

Question: how long should the AC run when first turned on

Anon said

when you turn on the AC for the first day of summer or heat how long would the unit circulate air then when does it stop

Reply:

The length of time that the A/C will run depends on many factors including

- the thermostat set temperature

- the building temperature at time the A/C is tuned on

- the efficiency of and cooling power (BTUS) of the system

- where the air is delivered

- thermostat location

- the thermal mass of the building: what materials have been heated up and need to be cooled down

- the heat gain rate of the building

- outdoor temperature, wind, and sun exposure

The air will circulate and the A/C will run until the thermostat is satisified. If the system cannot satisfy the thermostat for any reason the system will keep running.

Question: AC Fan runs 5-10 minutes then stops

(June 14, 2014) Scott said:

AC system starts (cools, fan runs, etc.), fan runs for 5 to 10 minutes then stops. No circuit breaker trips or electrical issues at the panel. Should I replace the fan motor?

Question:

(June 16, 2014) amit said:

Please help, My AC compressor starts when i power it on and works perfectly but cuts off prematurely within 5 min. Compressor starts only after 2 hours however fan runs continuously. I also tried switching off and on but of no use.

Had there been a problem in the compressor, why its working fine for 5 minutes after approx every two hours. Also You can understand that within 5 minutes thermostat also can't cut as cooling of room is also partial. please help I

Reply:

Amit

Possibly the motor is overheating, then binding, drawing high current, shutting down. Try cooling the outdoor unit with a water spray.

If cooling the outdoor unit (designed to tolerate rainfall) changes its operation that is probably a diagnostic clue.

 

Question: where to buy a replacement control for a sticking Amana AC contactor relay

(June 21, 2014) Joey Payne said:

Older Ammana unit still runs and cools well contact sticks and overheats. Sticking causes outside unit to continue to run contact burns and burning wire.

Reply:

Perhaps your HVAC supplier can offer a generic replacement relay or entire control

Question: water at the base of the compressor

(June 30, 2014) Anonymous said:

Is it normal for there to be water coming out of the base of my compressor

Reply:

Anon

Water at the outdoor compressor condenser is probably coming from melting ice or frost. If you see cycles of significant ice or frost build-up the refrigerant charge or metering may be incorrect and I'd ask for a check by an HVAC tech.

Question: Window AC unit keeps automatically resetting its temperture control up to a high number

(3 days ago) Mary said:

Why would my window unit automatically keep going up to 86 degrees?

Reply:

I don't know, Mary. If you mean that a manual control is changing its setting from where you set it I suspect someone else is involved.

Question: how does a low refrigerant charge cause the coil to ice-up

7/11/14 Bob said:

How does a low amount of refrigerant entering the evaporator coil cause it to ice up?

Reply:

Bob, low refrigerant means too little in the cooling coil, lower evaporation temperatures, ice formation. Details of the explanation begin at

FROST BUILD-UP on AIR CONDITIONER COILS

And at REPAIRS for FROST / ICE on COIL we include a more technical explanation titled

Reader Question: why does a low refrigerant charge cause frost to show up on the coil ?

Question:

(July 13, 2014) Anonymous said:
i have a Carrier heat pump that i cant get the blower to come on. I have replaced the board and thermostat and not sure what to do next. Any suggestions?

(Aug 2, 2014) Lou said:
I have a carrier condensing unit that the compressor wont start.I have voltage at the contactor and have replaced the start cap and run cap.odd to say,im drawing 11 amps on start and run wires coming from the contactor but i hear nothing from the compressor! any suggestions?

Reply:

Lou

Check for a bad start relay

Question: how to monitor energy use on a shared AC unit

(Aug 11, 2014) Michelle Mell said:
I live in an apartment...home that was converted to two units. We share the outside AC unit. We each have our own thermostat.

Is it possible to seperate so that each of the two units pays for their own electricity with that one AC unit? I mean can the power be split so to speak so that each apartment unit only pays for the cooing for their apartment?

Reply:

Michelle

In Europe energy use monitoring by individual apartment is required by law. If you live in the U.S. or Canada or Latin America that requirement is not given. A landlord could add equipment to monitor the time your thermostat calls for coolingh but that'd be an uncommon level of detail.

Question: compressor won't run until it's cooled down

(Aug 14, 2014) Andre Matthew said:
my AC is not cooling well don't know the problem with that.

(Aug 21, 2014) Wayne said:
When unit is cold it will start and run. After an hour the cooling fan stops but the compressor continues for a short time then quits. It will continue to start but will not start and run until it cools down.
Any ideas?

Reply:

Look for an overheating fan motor, relay or control board or possibly a refrigerant metering valve that is sticking.

Question: service tech says it may take hours after repair before cool air comes out of the system

(Aug 23, 2014) Anonymous said:
I just had a bad capacitor replaced in my Trane heat pump. Technician said it will take 7-8 hours before it begins to blow cool air. Outdoor compressor and fan are running, but air blowing out vents is still warm. Does it seem right that it would not blow cool air pretty quickly?

Reply:

Anon

I don't blame the service tech for being conservative - not wanting to be called back unnecessarily, but I'm surprised that she thinks it's going to take 8 hours for a heat pump to blow cool air.

It might take hours to cool down a hot humid house and it can take some time to cool down even hot ductwork, but cool air ought to be coming out of the supply registers within less than an hour of turning the system on - just giving time to get past the effects of hot ductwork and air handler parts from having sat off for a time.

I suspect that 7-8 hour guess was more designed to give the service tech time to get out of town.

If after 20 minutes (I'm going out of town too after this note) NO cool air is coming out of your supply registers, call the service manager of your heat pump repair company and politely ask for some more experienced advice.

Question:

(Aug 27, 2014) paris said:
i have problem with my air condition unit...i replace motor... conect capasitor with 2 wires from motor... and black to black and purple to nutural and one purple from compresor to capasitor ..the fan starts but compresor is not working ..did id id anything wrong

(Sept 2, 2014) Anonymous said:
John Powers:

I live in Thailand and in very heavy rain the rainfall off the roof of the house splashes down hard all over the compressor, even from the side.

The only way to prevent it would be to install a lot of spouting or move it to a southern exposure. Is it necessary? I have used it almost 24 hours a day for 3 years, and it works fine, though when repairmen recently cleaned it, afterwards there was a mildew smell, which eventually went away.

my handler has sweat and condensation on the outside

Question:

(Sept 21, 2015) Edward Bunn said:
Zone v. Phase
I have a heat pump. It is set up and has always operated as a two-zone system. One zone is upstairs and the other is down stairs. Each zone has a separate thermostat.
I just purchased a replacement pump for $7,000. I purchased a SEER-18, which is a high efficiency system.

I understand that what makes it efficient is that is operates in two phases. Initially, it starts up at a lower power before powering to a higher power, thus saving energy and money.

The installer now tells me that he needs another $1,500 to get the phases to work. First, he said the new system did not have a zone board (zone issue), which I priced on the internet for $169. Now, he says he needs to install dampers, which only controls the amount of air flow to a space (zone) and cost less than $75 (Home Depot).

Dampers really just control the amount of air in a particular zone of the home. These are already in my home. They relate to air zones and not start-up power. In my case, they control the air flow alternatively for the air upstairs and downstairs.
What am I missing? Am I being conned?

Reply:

I would ask for help from the service manager.

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

I've a Lennox outside a/c unit. The fan/motor and compressor are part of the unit. The fan was not spinning and the A/c is not running. I've isolated the problem down to the fan/motor or the compressor, but don't know how to check or find out which it is. Any idea on how to check if the fan/motor is 'bad' or the compressor is 'bad'? - Fan or ... 7/23/11

Reply:

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

Question: Our new AC won't keep running

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

Reply:

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

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

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

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

Reply:

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

Question: our A/C compressor tries to start but then shuts right back off

I turned my AC on and noticed it wasn't getting cooler inside, I went out to the condensing unit and the compressor tries to kick on but then shuts right back off. Can not having enough refrigerant cause this? If not what's the deal? - Derek 8/22/11

Reply:

Derek, as another reader commented, your compressor/condenser may be having trouble starting. A start capacitor can sometimes fix this problem and give some added life to the unit.

Not having enough refrigerant would not itself prevent the compressor from starting, though there are some more technical connections one could draw (low refrigerant, sticking thermostatic expansion valve, high head pressure can mean hard starting - but that's not where I'd start).

At REFRIGERANT FLOODBACK, LIQUID SLUGGING we explain how liquid refrigerant entering a heat pump or air conditioner compressor motor can destroy it and we discuss the recommended time that the system should be LEFT OFF if was switched off while it was running

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

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

I have some more info on my a/c when the a/c is turned on by dropping the temp in the house the compressor turns on but the fan does not turn, if you start to turn the fan by hand it starts spinning. When I turn it off by picking up the temp it stops.

When I drop the temp again nothing goes on. If I wait a few minuites and try it again the compressor starts but the fan still has to be started by hand. Thanks for any help you can give

Reply:

Henry I suspect a bad fan start-run capacitor.

Question: no air is coming out of our supply registers

I have a coleman unit. Had heating probs 2 years ago leading to complete computer panel replaced, evaporator coils cleaner, gas regulator replaced. Two days ago, my A/C decided to stop working. I hear the freon flowing into the coil region, the fan outside is turning, but no air is coming out of registers. What can it be? - Cheryl 9/9/11

Reply:

Cheryl if you have no air coming out of supply registers the blower fan is not working or the duct system has become disconnected or blocked. Coil ice-over in the air handler can also block airflow. Start by determining that the blower is running and that the air filter is clean.

Question: water at the air return vent

what makes the water from an airconditioner build up in the return vent? - Connie Woyan 9/15/11

Reply:

Connie: if you see water at the return vent it may be condensation on a cool surface, or it could be condensate leaking down into the return vent from your air handler. You'll need to make a closer inspection of the air handler (blower unit) itself.

Question: what type of copper is used in HVAC refrigeration piping or tubing?

What is the content of copper tubes used in AC? (i.e I would like to know the contents of pipe which is being connected between the Fan and compressor of split AC) - Pratik Shah 10/1/11

Reply:

Pratik

Copper tubing used in A/C systems for refrigerant piping is just that. Soft flexible copper piping. While the differences between K, L, M and DWV copper piping are primarily in wall thickness, the the copper tubing alloy class may also vary for flexible copper tubing used in HVAC applications such as refrigerant piping and oil line piping.

1/2" K copper tubing has a wall thickness of about 0.049"

1/2" L copper tubing has a wall thickness of about 0.040"

1/2" M copper tubing has a wall thickness of about 0.028"

1 1/4" copper DWV piping has a wall thickness about the same as L copper or about 0.040"

The flexibility of copper tubing also depends on how it was produced: annealed vs drawn. Annealed copper is softer, suitable for flared and compression fittings, though it can also be soldered with proper edge smoothing/rounding.

Drawn copper is generally used for soldered fittings though drawn copper types A and B tubing can be joined with some types of compression fittings as well.

Details about the alloy mix of various copper piping materials is given by standard ASTM B88 and are providedin exhausting detail by copper dot org.

Question: no sweat on the suction line

what could be the problem when the sunction line of an air conditioner is not sweating? - Diana 2/3/12

Question: hard starting compressor

jon- ac system is less than a year old, when I turned on ac to check, condensor comes on then shuts back off, then 30-45 seconds after comes on again for 2-5 seconds. Whats wrong? - Jon Anon 8/18/12

Compressor on Lennox centeal air not turning even if the thermostat is activated.. It is blowing warm air.
Possible problem - Roger 7/8/12

Reply:

Anon: regarding your hard-starting compressor/condenser unit: we can't with confidence say what's wrong with so little information - your service tech can diagnose the problem, probably fairly quickly.

But a common cause of the symptoms you describe is a bad start/run capacitor or worse, a failing compressor motor.

Todd said to Roger:

Rpger...not a professional myself but I had the same issue. The motor on my outside unit had worn out to the point that it needed to be replaced. Forturantely for me it was under warranty from a unit that I purchase 4-5 years ago. This might be strange for most units but we've had some above average summers here in Texas the last couple of years.

Another thing my HVAC tech does is check and replace the capacitor if necessary...I've been told that if the capacitor is shot, it will expand, almost resembling a coke can that is about to explode. Good luck.

Thanks Todd.

Roger, presuming you checked tonassure the unit has power and the thermostat is calling for cooling, if the suggestions in this article didn't get your system diagnosed check the LOST COOLING article linked above at the ARTICLE INDEX the bottom of this article - Editor

Question: does it help to spray the compressor/condenser coils when it's hot outside?

Does it help to spray water on the compressor coils when the outside air temp. is 100+? The inside air is going up in the afternoon to 82. - Greg Warner 7/7/12

Reply:

Some readers have reported that their compressor was overheating and ran ok when water cooled - this is perhaps a diagnostic step but not a reasonable repair. And don't soak electrical components.

Question: oil in the capillary tube? - recurrent cap tube clogging

i have replaced my compressor from company and when i started it was giving cool air but the copper pipe out side (large) was not cool enough and after 40 mints its timer light flashes and after 10 more mints its down automatically. it happens again and again i sent back it to company technician is looking into it. He said oil was in capillary and it needs flushing so he will replace its capilary since after cleaning its not fixed. do u think there is no fault in compressor? or what possibly is the problem.. - Wagar 7/11/12

Reply:

You'll want to check the installation manual to find the control light decoding for your brand and model of cooling equipment. Could be a control or control board problem too. It's just about impossible to flush a cap tube so replacement is normal. But if there is debris in the system, or excessive oil, the new cap can clog as well; good practice would be to empty the system, pull a vacuum, flush the whole system, install a filter dryer, replace the cap tube, and recharge.

Question: A/C not cooling, condenser fan not running

Several days ago I noticed that even though my air handeler was rinning the AC was not cooling, I foudn that the condensor was not turning,

I flipped the breaker (that apprered to be in the on position) and it worked for awhile. 15 minutes later I noticed that the condenser was not operating again so I flipped the breaker again it corrected the problem.

I then went on the replace the breaker which seemed to correct the problem, the AC worked normally for several days. Now I find the condenser is not working again and flipping the breaker fails the correct the problem. When the condenser was working it was providing good normal cool air.

The system is 2 years old. I assume I have an electrical problem in the condenser. What is likely to cause this problem and how can I test for it (I have a test meter) but I want to be careful because I know that a coil can retain a dangerous electrical charge even when all power is off and disconnected. - Rick 7/13/12

Reply:

typically we see if the fan spins, if it has power, and if the controls and fan contactor are bringing power to the fan when the condenser unit starts up.

Reader Followup

My problem turned out to be a bad contacter (damaged by ants) - Rick 7/13/12

Question: loud cricket chirping sounds at the compressor/condenser unit, and slow starting

outside unit making loud cricket sounding noise when running. Takes long time to come on when temp set low. - JT 7/276/12

Reply:

JT NOISE AIR CONDITIONER / HEAT PUMP provides noise diagnostics.

About taking a long time for the A/C to "come on" when the temperature is set low: the thermostat is operating like an "on-off" switch that turns the air conditioner system on and off in response to room temperature.

It's not an accelerator. So if there is an operating problem related to the system controls, the number of degrees below the room temperature to which the thermostat is set should make no difference in how long it takes the A/C system to start.

As long as the SET temperature is lower than the room temperature the cooling system will turn on.

Question: Why is my A/C not producing enough cool air?

A/C not producing enough cool air - I had my air conditioning system gassed 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. outside is reaching mid 90"s it's getting up to 80 in the house. Is my duct work screwed up? How do you repair trailer metal ducting? - Amanda

90 degrees outside and 83 inside with thermometer at 76. Cools off to 76 when sun starts to go down and house then gets cold. New capacitor and condensor just put in. Help. - Ginny 5/17/12

Reply:

Amanda: if your system is not cooling there could be any of a number of problems - see the article above as a place to start. If your basic complaint is that the A/C temperature at the supply registers is cool enough but the volume of air flow is too weak, we'd start by:

Weak air conditioner air flow - is there a relationship between refrigerant charge level and weak cool air flow rate?

Les said: Weak air conditioner air flow: Our A/C 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!

See DUCT & AIR FLOW PROBLEMS

(mod) said:

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.

Weak air Flow traced to Clogged Air Filters: Can Clogged Air Filters Affect the Room Thermostat?

(May 13, 2011) Jim said: If air conditioner filters are clogged will it cause the thermostat to shut off?

Jim: clogged A/C filters won't cause a room thermostat to shut off. The thermostat responds to room temperature. However clogged A/C filters that reduce air flow, cause coil frosting, or otherwise reduce or stop the flow of cool air into the room where the thermostat is located would mean that the thermostat would remain "un-satisfied" and should mean that the thermostat says "on" - continuing to call for cooling. See AIR FILTERS for HVAC SYSTEMS

Air Filters & Cooling System Amperage Draw: Could Removing the Air Filters Cause the Electric Motor in the Air Handler to Draw Higher Amps?

Question: got one for you. i put an ammeter on my air handler and it read 8.25 amps, I removed the filters and it went up to 9.75 lmao at the situation the amperage should have gone down. what gives here

Reply: causes of variations in electric motor efficiency and current draw measured in amps

Lost: this amps variation is beyond my expertise, but in general reducing the load on an electric motor will show up as lower amps or current draw, not higher amps.

Here are two interesting explanations of amps or current variations on an electric motor that I found when researching the question:

1. Voltage variations and current draw at electric motors: If your supply voltage is varying from your power company that can show up as higher amps draw on the motor (though it's a suspicious coincidence to see it exactly when you removed the filters and supposedly reduced the load on the motor).

Quoting from motorsanddrives [dot] com: "The effect of low voltage on electric motors is pretty widely known and ...

The amount of power the motor draws is roughly related to the voltage times current (amps). Thus, when voltage gets low, the current must get higher to provide the same ... To summarize the situation, low voltage can cause high currents"

2. Load variations and electric motor efficiency: A second possible source of seeing higher amps or current draw on your blower motor when you pulled out the air filters and thus reduced the load on the blower motor might be illuminated by this

U.S. DOE pamphlet "Determining Electric Motor Load and Efficiency"

- Quoting: "Most electric motors are designed to run at 50% to 100% of rated load. Maximum efficiency is usually near 75% of rated load.

Thus, a 10-horsepower (hp) motor has an acceptable load range of 5 to 10 hp; peak efficiency is at 7.5 hp. A motor’s efficiency tends to decrease dramatically below about 50% load."

Question: what causes warm suction lines in an air conditioner or heat pump system? Warm A/C suction line (should be cold) and zone control dampers that stopped working

JMONTE said: warm A/C suction line question: 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

Reply:

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.

See OPERATING TEMPERATURES HVAC.

Becky, 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.

See ZONE DAMPER CONTROLS

Becky said: motorized air conditioning zone dampers not working

My house has "zone" control with dampeners to close off the upstairs over the garage room unless that thermostat 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? silicon glued properly?


...

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

Or see COMPRESSOR / CONDENSER DIAGNOSTIC FAQs-2 - more-recent questions & answers about diagnosing compressor/condenser problems

Or see these

Recommended Articles

Suggested citation for this web page

COMPRESSOR / CONDENSER DIAGNOSTIC FAQs 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

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.

Comment Form is loading comments...

 

IF above you see "Comment Form is loading comments..." then COMMENT BOX - countable.ca / bawkbox.com IS NOT WORKING.

In any case you are welcome to send an email directly to us at InspectApedia.com at editor@inspectApedia.com

We'll reply to you directly. Please help us help you by noting, in your email, the URL of the InspectApedia page where you wanted to comment.

Citations & References

In addition to any citations in the article above, a full list is available on request.


ADVERTISEMENT