Short on-off cycling of air conditioner or heat pump compressor/condenser unit questions & answers:

FAQs help diagnose the causes the A/C or heat pump fan condenser unit that keeps cycling on and off rapidly

This article series explains how to diagnose an air conditioner or heat pump that is not cooling: this article explains how to diagnose and correct air conditioning problems like lost or reduced air conditioner cooling capacity, reduced or no cool air flow, reduced or no actual lowering of the air temperature, or an air conditioner that won't start.

Air Conditioner or Heat Pump Short Cycling Diagnostic FAQs

These questions & answers about why an outdoor compressor/condenser unit is turning itself on and off too frequently were posted originally

at SHORT CYCLING AC COMPRESSOR - topic home.

Sketch: short cycling Copeland scroll HVAC compressor motor cycle pattern, discussed in detail below on this page.

 

Question: My Air Conditioner (or heat pump) keeps cycling on and off too rapidly - what might be wrong? short A/C on-cycle problems

Joe said: short cycling air conditioner compressor diagnosis: I have the same problem as Mathew: my A/C compressor cycles on and of every ~10 seconds. I is about 5yr old. What can we do to fix this system. Please help. Thanks!

Matthew said: short cycling air conditioner problems: Our air conditioning compressor cycles on and of every few seconds or minutes. What can we do to fix this systems not even a year old

Reply by (mod)

Five causes of a home air conditioner compressor short cycling on and off too rapidly - Short Cycling Air Conditioner Diagnosis & Repair

DanJoeFriedman (mod) said to Joe and Matthew (re questions just above):

1. Loss of air conditioner refrigerant -
   
   a refrigerant leak in the system. You may be able to repair the short cycling problem temporarily by recharging the air conditioning system but the proper repair is to find and fix the leak.
   
   Otherwise you will have to keep repeating the costly service call to just add refrigerant.
   
   See REFRIGERANT LEAK DETECTION.
2. A/C Coil Icing -
   
   the evaporator coil (cooling coil) is iced over (such as due to improper refrigerant charge or dirt or a reduced air flow due to a dirty filter) - take a look in the air handler to see if the coil is blocked by ice or dirt.
   
   See FROST BUILD-UP on AIR CONDITIONER COILS
3. Oversized air conditioner -
   
   if the short cycling has always been a problem since the day the system was installed, there is a good chance that the unit is too big (too many BTUS) for the space being cooled.
   
   A more subtle version of this same problem is that you've done something like closing doors or adding a partition that had the effect of reducing the size of the space being cooled.
   
   Sometimes we can mitigate this problem by running the blower fan at a lower speed or by opening interior doors to increase the size of the space being cooled or even by moving the thermostat.
   
   See AIR CONDITIONER BTU CHART and OPERATING TEMPERATURES HVAC
4. A/C control problem -
   
   it's less likely, but a damaged control board or switch could also be causing rapid equipment on-[off cycling.
5. Compressor damage or compressor start-troubles: -
   
   I 've seen these other causes of air conditioner short cycling: if someone manually turns the air conditioner thermostat up and down or on and off too frequently, a hard-starting compressor may find that it has been shut down with high internal head pressure inside the compressor.
   
   Normally that head pressure bleeds off over time, making it easier for the compressor to re-start (against low head pressure) the next time it turns on.
   
   See HARD STARTING COMPRESSOR MOTORS

But if someone is turning the system on and off quickly, the compressor may have a hard time re-starting against the pressure on its outlet side. A starter capacitor addition or replacement might fix the problem. If your A/C compressor is showing this symptom but works OK if you leave it shut off for 30 minutes or longer, that may be the trouble.

We have also see or a damaged compressor internal refrigerant valve causing high head pressures;

In sum, you need a service call from a professional to correctly diagnose and repair the problem. Ask the service tech what she/he found and let us know - what you find will help other readers.

If your air conditioner or heat pump has the opposite problem, staying on too long,

see LONG-ON CYCLING AC COMPRESSOR.

 

Copeland Scroll Digital compressor cycling vs. HVACR compressor motor short-cycling on and off

It's possible that the unit is equipped with a digital scroll which is actually used to prevent short cycling by allowing the machine to reduce load significantly. The scroll is opening and closing to match the building load rather than shutting off and coming back on.

If the unit never sounded like this before it’s likely the circuit has gone low on refrigerant which causes the sound to become louder.

The digital scroll can also be turned off to operate like a regular scroll if the noise is unbearable.

Thank you, - On 2018-05-08 by markk1pe -

Reply by (mod) - Copeland Scroll Digital compressor cycling vs. HVACR compressor motor short-cycling on and off

Thank you for the comment, Mark, that;s interesting,

It is not clear why a digital scroll compressor would be cycling on and OFF every few minutes. If I have understood the material correctly, Emerson's article on the operation of the Copeland Scroll Digital compressor that you kindly referred describes capacity cycling but doesn't say that the motor actually turns on and off.

Excerpts:

The Copeland Scroll Digital™ compressor increases HVAC system efficiency by precisely matching compressor output to your heating or cooling needs which saves energy and reduces maintenance costs.

Developed in 1993, the first application of this technology was in refrigerated marine containers in 1999. In 2000, the air-conditioning version of this technology was first launched in Asia. Today, over one million pieces of these compressors are working in the field all over the world ...

A cycle time consists of a "Loaded State" time, and an "Unloaded State" time (Figure 2). [shown above]

The duration of these two-time segments determines the capacity modulation of the compressor.

For example, in a 20-second cycle time, if the loaded state time is 10 seconds and the unloaded state time is 10 seconds, the compressor modulation is (10 seconds x 100% + 10 seconds x 0%)/ 20 = 50% (Figure 3).

If for the same cycle time, the loaded state time is 15 seconds and the unloaded state time is 5 seconds, the compressor modulation is 75%.

The capacity is the time averaged summation of the loaded state and the unloaded state.

By varying the loaded state time and the unloaded state time, any capacity between 10% and 100% can be delivered by the compressor.

- source: How Copeland Scroll Digital™ Works, [PDF] Emerson Climate, Website: http://www.emersonclimate.com/, retrieved 2018.05/08, original source http://www.emersonclimate.com/asia/en-ap/products/compressors/scroll_compressors/commercial/copeland_scroll_digital/about_copeland_scroll_digital/pages/how_copeland_scroll_digital_works.aspx

Illustrated above illustrates cycling the capacity of an Emerson Copeland Scroll Digital™ HVACR compressor motor:

Live link added 2024/07/26 REFRIGERATION - CONTROLLING DIGITAL SCROLL [PDF] - orignial source https://www.copeland.com/documents/refrigeration-controlling-digital-scroll-technical-information-en-gb-4214506.pdf

Excerpt:

Refrigeration applications such as retail and convenience stores are requesting more and more a system able to cope with varying load fluctuations especially with regard to efficiency, as energy costs continue to rise as a direct subsequence to environmental awareness.

 

Other HVAC Compressor/Condenser Unit Short Cycling Questions

On 2020-09-13 by Daniel - Compressor/condenser shuts off after 7 minutes

In south tx have thermostat set to 70, outside unit runs for 7 minutes then shuts off for 20 minutes is that ok?

On 2020-09-13 - by (mod) -

Daniel

Check your room or control thermostat; if the AC unit is shutting off because the SET temperature on the thermostat has been reached, that's normal and OK;

If it has not gotten close to the set temperature then the compressor/condenser may be overheating.

 

On 2020-07-13 by Aaron

After my unit shuts off the air handler continues to run for a minute. Is that normal?

On 2020-07-1 - by (mod) -

Aaron

It is normal for an air handler to continue to run briefly at the end of an on cycle in heating mode.

It's most common when the system is being used in as it's desirable to purge heat from the heat exchanger, avoiding the risk of damage to the equipment. They may be some systems the do the same thing at the end of a cooling cycle.

On 2020-07-04 by Dave - very short on-cycles

We have a one year old Lennox 2 stage A/C. We noticed suddenly that it began short cycling... running for maybe 3 seconds and shutting off, then doing the same thing about 5 minutes later, and again running just a couple of seconds. The temperature inside though was OK, at 75 degrees which was the thermostat setting.

The next day, it worked fine without short cycling. The day after that, it began short cycling again.

A HVAC technician came the next day, when it was working fine, and he found nothing wrong. He surmised maybe the low stage is so quiet it was running continually, or something, that didn't make sense.

It's started short cycling again, and this time the temp went up to 77. Then it started working again. It's very frustrating as it seems we might be damaging this one year old unit.

On 2020-07-04 - by (mod)

If you're really seeing very short on-cycles then I agree it's worth further troubleshooting. Perhaps a polite conversation with the HVAC service company's service manager will get you a tech experienced with the issue.

Sometimes it's a dirty expansion valve or other control that misbehaves intermittently and of course behaves perfectly when the repair person is on site.

 

On 2020-06-28 by Christine - Air Conditioner shuts down in very hot temperatures

A/C turns off during the hottest part of the day for two+ hours.

On 2020-06-28 - by (mod) -

Christine

Some AC systems include safety controls that will shut the system off to prevent more-costly damage from, for example, overheated components or excessive refrigerant pressure.

So I suspect your system, when it's working hardest, has a component that's overheating or otherwise causing a condition that shuts the system down.

An experienced A/C service tech can track down the failing part.

 

On 2020-06-15 by Teresa - air conditioner seems to be short cycling

My air conditioner seems to be short cycling. Yet it has a thermostat which has a automatic compressor protection delay to avoid potential damage to the system. At least that’s what the thermostat manual says . So why would it be short cycling ?

On 2020-06-15 - by (mod) -

Teresa,

With no more data I can but guess that the short cycling compressor is due to one of the causes in the article above, perhaps a bad expansion valve.

 

On 2020-05-22 by fred - heat pump compressor turns off randomly

heat pump compressor turns off randomly but fan keeps running

On 2020-05-22 - by (mod) -

If not one of the causes above on this page, perhaps a bad relay, control, or even a loose or bad electrical connection.

 

On 2019-07-12 by Susie - My electric bill is increasing 30-40 every month

My electric bill is increasing 30-40 every month. Has tapered off after four months. New home. New a/c. Six other new homes, same size or larger, with more people, thermostat set much lower with electric bill 40 or more dollars less. Ac company cannot find anything. Electric company said my cooling percentage is too high.

On 2019-07-14 by (mod)

Perhaps an expert electrician onsite making amps checks can find the problem.

Watch out, there may be safety or shock hazards.

 

On 2019-05-17 by Richard D.- burned wiring, now AC unit short cycles

Last year at the end of the summer my AC unit burnt the T-1 wire off the top of the Contactor. I didn't repair it until this year. I replaced the terminal end and started it up and now it's short cycling. I will run about 30-45 seconds then shut off for about 1 or 2 seconds then immediately start again an repeat the symptom. Any thoughts on this would be greatly appreciated.

On 2019-05-18 by (mod) -

Do you think that replacing the burn to terminal actually corrected the problem that caused the burn up? I can't tell from the text. You might want to go through this with Justin's for short cycling given in the article above on this page.

 

On 2018-12-07 by Gary- blower cycles every 30 seconds

What will cause a blower motor to cycle every 30 seconds yet run smooth when the aux heat is used. When the thermostat calls for a 1 or 2 degree rise in temperature the blower motor short cycles but when the thermostat call for 3 degrees or more it doesn't short cycle until the thermostat setting is within 2 degrees. Than the short cycling begins

On 2018-12-08 by (mod) -

probably one of the reasons given in the article above.

Watch the temperature dial in the fan limit control switch as the furnace goes through a cycle and let me know at what temperature the dial is pointing and which direction does it moves when you see the short cycling.

 

On 2018-11-14 by Terry - why does heat pump turn on and off too frequently?

What will make your fan on a heat pump cut on and off

On 2018-11-15 by (mod) -

Possibly a problem with the defrost cycle.

 

On 2018-08-30 by Joe- AC unit runs 5 minutes then I smell something burning and it shuts off

Ive been noticing the smell of something burning the past 3 days now it's hot as hell in here. I went outside to see if the unit was running and noticed the unit only runs 5 minutes then it stops.

On 2018-08-30 by (mod) -

Joe

On the chance that the burning odor is from an electrical or motor or HVAC equipment failure there is risk of a fire. Sorry to say you should turn the equipment off at its circuit breaker or fuse, then call for repair.

Smell of something burning at my air conditioner

Ive been noticing the smell of something burning the past 3 days now it's hot as hell in here. I went outside to see if the unit was running and noticed the unit only runs 5 minutes then it stops. On 2018-08-30 2 by Joe -

Illustration: the capacity cycling model for a Copeland Scroll digital compressor discussed by Emerson and cited below. [

Reply by (mod)

Joe

Watch out: On the chance that the burning odor is from an electrical or motor or HVAC equipment failure there is risk of a fire. Sorry to say you should turn the equipment off at its circuit breaker or fuse, then call for repair.

 

You can save repair cost by deciding to leave off the anti-short-cycling control - a safety device ?

The anti short cycling device shorted out on the outside air conditioning unit. The service tech wired around it and said I didn’t need to replace it if I didn’t want to spend the money. Question: Do you think it needs to be replaced? He said some of these units are made without one. On 2018-08-20 by Martha

Reply by (mod) -

Martha

I am not smarter than your on-site technician, but I speculate that she's saying you can save repair cost by deciding to leave off a safety device designed to protect the compressor from damage that can be caused due to other problems that show up as short-cycling.

Whose judgement do we prefer: the original installer, the manufacturer (if the short cycling device was part of the original equipment), or the tech who's saving you money?

If the compressor unit is over-sized it will cool adequately but won't run long enough to dehumidify.

I recently had a 3 1/2 T Payne Dual HeatPump/AC installed in Dec 2017. Heat worked perfectly. However in early July the compressor went bad. The air compressor was replaced with a new one. Since the new compressor has been installed it is cycling 5 minutes on and 20 min off.

The temperature is cooling; however the humidity in the house has varied from 50-58% in 90-100 degree temperatures. Service tech checked unit for 2 hrs. He stated since the compressor was cooling everything was ok. I don't agree with him and I don't think he knows how to fix it. This unit is still under warranty. Actually only used 6 months. - On 2018-07-20 by Lilian

Reply by (mod) -

Lillian

If the compressor unit is over-sized it will cool adequately but won't run long enough to dehumidify.

On 2018-07-10 by Todd

Hello, i have an older 2.5 ton split heat pump in a So Cal dessert area. Condo is 1200 sq ft and well insulated being built w block and 50% of condo is somewhat sub terrainian. The unit cools adequately yet only has 6-8 degrees diff between hi and low lines.

My question is: after 5-6 hours of operation holding 76f indoors w 109f ambient temps. The inside temp all of a sudden begins to rise as if the system has shut off. I keep the air handler on all the time just for circulation.

Once I realize the AC is not working, I turn off the AC at the thermostat, wait 1-2 minutes, turn it back on and it immediately goes right back to holding the 76f set point for the rest of the day.

I have the condo in escrow and need to have a tech out to service the unit. Any idea what may be causing this every 5-6 hours or what can I tell him to check if he doesn't know?

Thank you so much !

On 2018-07-05 by Hipe

My ac unit was charged several weeks ago. It worked fine until it got extremely hot now the condenser fan is kicking on and off every few seconds. would a overcharged system cause this

On 2018-07-05 1 by (mod) - If only the fan is turning on and off and not the compressor motor

Hipe

If only the fan is turning on and off and not the compressor motor itself then I suspect it is a problem with the fan relay or control.

However if the entire unit is switching on and off it is possible that debris or frosting in the thermostatic expansion valve that meters refrigerant is causing the valve to stick which in turn on some compressor systems will shut off the compressor in response to high-pressure.

On 2018-06-30 by Todd Jacobs - AC blows very cold but outside unity is short cycling

My ac is blowing cold very cold but in a cooling cycle the outside unit will turn on for 5 min or so and then turn off and on immediatly for another 6 minor so then off then on again is this a short cycle but its cooling the home

On 2018-06-30 by (mod) - I think I have a short-cycling heat pump.

Sounds like it to me

On 2018-06-24 by tim

I think I have a short-cycling heat pump. It is essentially new (new build 1600 sq. ft. home 6 months ago).

It is a 30,000btu (2.5 Ton heil system) Since we went into the cooling season we have had nothing but problems with it, from not running to fan only operation, to not removing humidity sufficiently. The installer was confused as to what the problem was so finally a rep got involved. (low amp draw, low pressure were some of the things I heard being talked about)

The only actual things they have done is: replaced capacitor, adjusted low pressure and recently another rep decided is was over-charged ( a tech on the phone with him thought it was a bad coil) so they removed refrigerant and then re-installed. The compressor comes on for 6-7 mins then off for 6-7 mins.

This is about 5 of these on/off cycles per hr. The OAT was 90 with 48 % humidity and my set point is 73 with a 64 % humidity level inside the house.Also, when the compressor shuts of the air handler continues to run for 4 more mins which is just blowing moist air into the house and humidity goes up until the next cycle. At night around 11pm with an OAT of 78 the on/off cycle is 5 mins on 8 off.

Personally I am starting to think it is too big of a system for my house as I had it super insulated with R50 in the attic and R13 in the walls.

The builder normally does R30/R11. His HVAC sub seems to have a standard install of 2.5ton systems in all the homes the builder builds.

I see that a 2000 sq. ft. 4 bedroom home he just built has the same system as mine, so I'm thinking if a 2.5 ton is sufficient for a 2000 sq ft home with R30/R11; it's over kill for my R50/R13 1600 sq. ft.. home....Any thoughts?
Thx

On 2018-06-22 by Shantanu Bandyopadhyay

My Hitachi 3 * AC runs normally at 28 degree. No cooling problem. But compressor starts every after 5 minutes. And run 3 minutes. When comp starts then only my computer UPS fails for fraction of second. Causing the computer reboot. APC 600 V UPS. NEW. 4 Sq MM wiring. No voltage fluctuations. Hopeless. Please suggest

On 2018-06-14 by Chris - Compressor cuts on and off every 5 seconds

We have a two and a half ton condenser and when we cut it on the compressor cuts on and off every 5 seconds and not cooling the house we just got to fix where they had a leak in the copper line in the air handler and he recharged it two weeks later it broke down and the compressor kicks on and off every 5 seconds and started not to cool the house what would be a problem can you bypass to make the compressor work and cool?

The fellow that fixed it the leak in the line said that all the oil came out in the air handler upstairs out of the line and made the compressor not work can I bypass that and how

On 2018-06-15 by (mod) -

Chris

YOu cannot bypass the compressor and have cooling, but you can leave the A/C compressor/condenser powered-off while you wait for repair, and during that time you can turn the air handler fan to ON so that you have some continuous air movement.

 

On 2018-05-23 y Rhonda - AC turns off after about 5 minutes

When I turn my a/ c on it turns off in about five minutes.what could be wrong.

On 2018-05-24 by (mod) -

Probably one of the things listed inSHORT CYCLING AC COMPRESSOR, Rhonda. I'm sorry but with not a shred of information about your system I can't make a smarter guess than what we've organized at SHORT CYCLING AC COMPRESSOR.

Please take a look and let me know if any of that is confusing.

D

On 2018-05-10 by Ron Betz

My outdoor heat pump AC will run smoothly for 2 day and then stop. It will restart if I hose it down. Recently had the fan motor changed but no the problem. Help, Thanks.

On 2018-05-11 by (mod) - overheating compressor

Certainly sounds like an overheating compressor. Before condemning the compressor motor I would want to know that the fan is working correctly.

On 2018-05-12 by Ron Betz

I will check it out. I had the fan replaced last year because of the same problem.The home warranty tech that replaced the fan seemed unsure of his trade. Thanks for your reponse and advice.

On 2018-05-04 by Jeff - AC compressor shuts off then re-starts every few minutes

Tks for the good troubleshooting.
My unit is able to cool continuously (compressor running, air handler blowing..etc) until the setpoint has been reached (say from 83F -> 78F).

However, once it reaches setpoint, then about 2 mins later it kick start the A/C for a few mintes, shuts-off, and then start for another few min... shuts off.. as if oscillating around the setpoint temperature.

Since it's able to bring temp down to 78F so I figure it's not low refrigerant or frozen coil as suggested in this article. It almost seems to be the thermostat is "too sensitive" trying to control on the littlest temperature deviation from setpoint.

This is a new Sensi Wifi Smart thermostat installed in Summer of 2017.
Any thoughts?

On 2018-05-04 by (mod) - AC compressor shuts off then re-starts every few minutes

If the problem began only after you install the new thermostat, and began immediately after you installed it, one would suspect an incompatibility or a wiring error.

On 2018-02-25 by Rog - causes of short cycling compressors

My unit want stay on no more than 10 seconds before cutting off then back on again

On 2018-02-25 by (mod)

Rog

The article SHORT CYCLING AC COMPRESSOR lists common causes of the problem you describe. Most likely that's not something a homeowner can fix; you're likely to need help from a trained HVAC technician.

Also see short cycling related to a defrost problem at HEAT PUMP OUTDOOR UNIT DEFROST CYCLE

 

On 2018-01-31 by CG - defrost cycle problems at the outdoor unit

my air condition/heating fan/condenser? outside when I put the heat inside on it stays on for 5 minutes then shuts it turns on again but the fan outside does not turn,,,I have to manually keep turning the unit off then after few minutes back on to get the heat to come on,, Air conditioner in summer works fine

On 2018-01-31 by (mod)

CG

That sounds to me as if the condenser unit is unable to start- possibly a defrost or failed heater or of course it could be some other problem. A heat pump system in most climates also has a backup heat that should run if the outdoor unit cannot (e.g. due to low temperature).

I would call for repair service. Let me know what you're told as that will help other readers.

See HEAT PUMP OUTDOOR UNIT DEFROST CYCLE

On 2017-12-30 by Bev S - New A/C Heat Pump shuts off after 5 minut4es

New A/C and heat pump installed, with this cold weather we have just used the heat. It goes on at desired temperature for 5 or a little more minutes. Then it goes off, am thinking it has reached set point. However, it starts short cycling on for 15 seconds off for 20 seconds.

To be honest it happens at night and I fall asleep counting the on and off cycling. Called company that installed unit. They want to charge us to put in a larger return duct. Does that sound right?

On 2018-01-02 by (mod) -

Perhaps I'm missing something but a reasom a need for more return air migjt be connected to short cuclimf wpuld be.am over heated oil.pr gas fires furnace hear exchanger. I. Unxlear how that would cause a het pump outdoor xpreasor condenser unit to short cycle.

What explanation was offered?

On 2018-01-03 by Bev - taking out a clogged refrigerant filter stopped short cycling compressor

@Bev,
Well I have taken the filter off/out and it does not seem to be short cycling. It is maintaining 78 degrees. Just going on and off every 10-15 minuets to maintain the the temperature.

So my FREE solution is no filter in the return line. This is a totally electric A/C Heat pump unit.

 

On 2017-12-27 by Bam - goodmen heat pump and it keep cutting on and off

I have goodmen heat pump and it keep cutting on and off it comes on for 5sec and back off for 5sec help??

On 2017-12-27 by (mod) -

Bam

The explanations for a heat pump that's short cycling on and off are given in SHORT CYCLING AC COMPRESSOR.

Yes there might be some other snafu that we haven't anticipated. So I'd ask for a service call from your service technician - you don't want the cycling to continue as the equipment is likelyi to be damaged. Turn it off, use backup heat, and call for repair.

On 2017-08-14 by Morteza - on-off cycling compressor unit traced to bad voltage control relay on unit in Iran

Dear mod, You are right,i opened the system and checked the phase and voltage control with a tester and understood that the incoming power had no problem but the control was faulty and was disconnecting circuit without any reason.

I changed it and now everything is ok.

Thank you Man,best wishes for you from Iran

On 2017-08-14 by (mod)

Great news Morteza. It is so satisfying when you can sort out a problem like a short cycling AC compressor. Thanks for taking the time to give us the feedback.

Daniel

 

On 2017-08-11 by Morteza - running cycle takes around 6 min but after around 2 minutes its compressor stops for 2 second and then restart again

My AC system works but there is a problem.Its running cycle takes around 6 min but after around 2 minutes its compressor stops for 2 second and then restart again,in each cycle this happens 2 or 3 times!

On 2017-08-11 (mod) -

Morteza, at we discuss some causes of A/C system short-cycling, as you might have read. beyond those causes, from just your brief question I don't know of a more-specific suggestion I could make other than to ask for advice from your service tech.

In my OPINION a system that is cycling on and off every few minutes and bouncing on and off every 2 seconds needs repair, perhaps just to a control or relay, and I add that while waiting for the service technician, I'd leave the system off to reduce the chances of more costly damage.

 

On 2017-01-29 2 by Steven hagewood - What keeps a heat pump from kicking on

What keeps a heat pump from kicking on

On 2017-01-29 by (mod) - What keeps a heat pump from kicking on

• Check first for power at the unit
• Then check the thermostat settings
• Then check the control boards/relays
  
  even a loose wire or corroded space connector can be at fault or there can be a more costly issue like a failed compressor motor

On 2017-07-04 by Anonymous - cleaning fixed the control

I cleaned it and it works fine now

 

On 2016-12-06 by Katy king - should compressor be running when on heat setting?

With central heat and air unit, should compressor be running when on heat setting?

On 2016-12-09 by (mod) - Yes if the system is a heat pump

Katy

If your system is a heat pump then if the outdoor air is not too cold for it to operate the heat pump compressor will run in heat mode

 

On 2016-11-24 by James - compressor gets hot and recycles

Compressor get hot n recycling quick

On 2016-11-24 by Anonymous Compressor get hot n recycling quick

James,

I agree that short cycling compressor could be due to one of the causes listed in SHORT CYCLING AC COMPRESSOR. There could also be simply a problem with a failing control.

But when the compressor motor is getting hot, I suspect also problems like a failing compressor motor, low voltage, or similar operating problem.

 

On 2016-09-13 by Deborah Campbell My outside a/c unit will cut on and run for awhile, then I'll hear it cycle through and shut off.

Having the same problem as Wesley:

My outside a/c unit will cut on and run for awhile, then I'll hear it cycle through and shut off. When I check the thermostat it is reading 75 with the air temp set on 71, the inside is still running while the outside unit is off.

Then the outside unit comes back on and runs for awhile again but shuts off after some time. You can feel the air coming from the vents and it feels cold but still stays hot in the house. Any ideas as to why the outside unit keeps shutting off

Anyideas. Both inside and oitaidw units are less than a year old.

On 2016-09-15 by (mod) - My outside a/c unit will cut on and run for awhile, then I'll hear it cycle through and shut off.

Thanks Steve. More likely it's the drain that gets clogged but indeed a float switch can foul up and stop working. Typically it gets replaced.

Deborah:

Overall: I'd like to see a compressor/condenser unit ON cycle time of 10-20 minutes. The length of time before the next ON cycle of the compressor/condenser unit isn't standard but it ought to be more than 5 minutes, perhaps 10 or more. The rate of heat gain, air leakage and other factors determine how quickly a cooled space heats-up again once the cool air flow stops. IN any event, 5 Minute on-off cycling is very likely an indicator of trouble.

It's possible for a residential air conditioning system to be operating normally when a compressor shuts off, then turns back on depending on the system's controls.

That's so if the "off" period is long - perhaps 10-15 minutes depending on weather conditions and system capacity. In moderate heat, 10 minutes on and 10 minutes off would not be abnormal but in my OPINION it's close to the edge.

A compressor motor that is cycling on and off rapidly is going to be damaged by that condition and depending on the system design, it may also ultimately have trouble re-starting against high head pressure in the system.

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

I think most HVAC techs (more expert than I) will agree that if we get down to 5 minutes or less on and off there is definitely a serious operating problem to be found and fixed.

But short-cycling on and off of an A/C compressor unit every few minutes (say 1-5 minutes) sounds to me like a diagnosis and repair are needed.

A second sort of "short cycling" of the compressor also suggests that diagnosis and repair are needed: if an air conditioner or heat pump compressor runs for a very long time (i.e. the cooling system is not able to reach the indoor set point on the thermostat) and the the compressor shuts off for just a few minutes, then re-starts, I suspect trouble. Causes include lost refrigerant, ice-blocked cooling coils, thermostat not working properly (blocked, in sun, in airflow, dust-crud clogged).

Another cause of short cycling is an over-sized A/C compressor. The unit cools down the interior space too quickly. One result is that it doesn't dehumidify adequately due to those short "on" cycles.

SHORT CYCLING AC COMPRESSOR suggests common explanations for on-off or short-cycling of an A/C compressor unit. Usually I think first of an overheating motor. That in turn can be due to a motor that's failing or to another cause such as low voltage; a bad control board or contactor are less-likely candidates but then your onsite tech may find something else.

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• SHORT CYCLING AC COMPRESSOR

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