Compressor/Condenser Unit Won't Stop FAQs

A/C & Heat Pump Outside Condenser unit won't turn off

Compressor / Condenser Unit Won't Stop Running FAQs

Diagnostic Procedure Articles:

• CONDENSER FAN WON'T STOP
• COMPRESSOR / CONDENSER DIAGNOSTICS - home
• HEAT WON'T TURN OFF - if your heat pump is in HEAT mode
• HVAC COMPRESSOR WON'T STOP

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A/C compressor won't stop running

I recently noticed my AC condenser unit still running when the system inside shutoff by itself. and also, does the condenser unit have to be leveled. I notice the slap which holding the unit is slopping. Any suggestions? Thank you. - Rick 8/16/11

Reply:

A/C compressor/condenser won't stop running:

Rick usually when an A/C condenser unit won't stop running even though the inside equipment has shut off by itself my thinking divides into two investigations:

- is there a problem with the INDOOR unit such as a blower fan that won't start, an access door switch open, a condensate drain switch turning off the blower unit - these can leave the system calling for heat and the compressor running (though that's not good for the compressor)

- is there a problem with the outdoor equipment such as a bad control relay or control board

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: how long should an air conditioner compressor run before it cycles off?

Hi. How long should my ac compressor keep on running before it automatically turns off. - Mon 5/31/12

Reply: it depends...

Mon: about typical air conditioning compressor run time, I don't think there is a single right answer to your question, because the on-cycle time depends on several variables that could in some cases leave the unit on for a long time, even continuously. Those variables that set the run time for the compressor include

- the indoor temperature, that is in turn affected by outdoor temperature and sunlight as well as building heat gain, windows, insulation, air leakage, and similar factors

- the thermostat set point - if the thermostat is set to a cooling number below what the system can achieve it will run continuously

- the size or capacity of the cooling system versus the actual building cooling load

However there is another way to approach your question that may be more useful diagnostically. That is to ask if something has changed in how your A/C system seems to operate.

So if you think that the building and its insulation, windows, heat gain conditions have not changed, and if your thermostat setting is the same temperature as in previous cooling seasons, and if the outdoor temperature and sun and wind conditions are similar to previous seasons, and THEN if your cooling system seems to run longer or continuously when it did not previously, there may be a problem to diagnose and repair.

Check LOST COOLING CAPACITY

for more detailed diagnostic suggestions.

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: 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: air conditioner or heat pump compressor / condenser won't shut off

My air conditioner compressor keeps running even when I put the thermostat on heat.

I just had a new furnace installed this winter and there are two wires coming from the compressor one is red and one is white.

I connected the whit to the letter "C" on the furnace and the red to the red wire.

I tried to connect the white wire to the yellow, green and white wires but the compressor would not energize.

When I connected the white wire to the "C" contact in the furnace the compressor came on runs fine and puts out cold air but will not shut down when I switch to heat? (Apr 29, 2015) Raymond

Reply:

First check that the thermostat is set above room temperature or is in the OFF position.

Then check your thermostat wiring connections to the control board in the air handler against the IO manual wiring instructions or wiring diagram.

Or for more help see THERMOSTAT WIRE CONNECTIONS - how to wire up all types and brands of heating & cooling thermostats

Then see COMPRESSOR / CONDENSER DIAGNOSTICS where we include HVAC COMPRESSOR WON'T STOP

Heat pump in emergency heat mode won't turn off

AC side works good air out @ 59-60 deg. When I switch to heat emergency heat mode, the heat comes on & blows hot air & goes well beyond set point & wont shut off until I shut it off .

I'm mot much good @ computers so help me if you can Thanks - On 2020-11-11 by tom -

Reply by (mod) -

Tom

When cooling works and heating mode does not I suspect a control board or reversing valve problem. That's what your service tech will probably check; it's not something a homeowner would try.

Most likely a control is turning on your backup heat and not turning it off - you're stuck in heat mode.

See the diagnostic steps at BACKUP HEAT for HEAT PUMPS 

Condenser unit slows but never stops running

Outside unit continues to run all day, periodically slowing for about 5 minutes, then clicking back to normal. It has been running for almost 48 hours straight.

Temps here today are going to be around -8 to -10° C. How can I stop this? On 2021-12-23 by SEM

Reply by Inspectapedia Com Moderator - nonstop running may be time for service

@SEM,

Best to shut down the unit entirely; you'll have to runon backup heat - assuming we're discussing a heat pump.

It's possible that the defroster on your outdoor unit is not working - or of course there could be some other cause as we haven't a shred of information about your installation.

I'd turn it off and call for service.

Comment by James

@SEM, if it’s a heat pump it will run constantly with the temps that low.

I have mine set to turn on Aux heat if it gets more than 2 degrees below the thermostat set temp. It’s probably to cold for the heat pump to keep up with the thermostat set temp.

You can set it to run simultaneously with the indoor heat on most systems.

I would measure the heat coming out of the vents with just the heat pump running and see if it’s putting out heat. The slow down is probably to defrost but you would need someone to look at it to be sure.

Question: My A/C compressor just won't stop running

I recently noticed my AC condenser unit still running when the system inside shutoff by itself. and also, does the condenser unit have to be leveled. I notice the slap which holding the unit is slopping. Any suggestions? Thank you. - Rick 8/16/11

Reply:

A/C compressor/condenser won't stop running:

Rick usually when an A/C condenser unit won't stop running even though the inside equipment has shut off by itself my thinking divides into two investigations:

- is there a problem with the INDOOR unit such as a blower fan that won't start, an access door switch open, a condensate drain switch turning off the blower unit - these can leave the system calling for heat and the compressor running (though that's not good for the compressor)

- is there a problem with the outdoor equipment such as a bad control relay or control board

See COMPRESSOR / CONDENSER DIAGNOSTICS

Question: My A/C compressor just won't stop running

I recently noticed my AC condenser unit still running when the system inside shutoff by itself. and also, does the condenser unit have to be leveled.

I notice the slap which holding the unit is slopping. Any suggestions? Thank you. - Rick 8/16/11

Reply:

A/C compressor/condenser won't stop running:

Rick usually when an A/C condenser unit won't stop running even though the inside equipment has shut off by itself my thinking divides into two investigations:

- is there a problem with the INDOOR unit such as a blower fan that won't start, an access door switch open, a condensate drain switch turning off the blower unit - these can leave the system calling for heat and the compressor running (though that's not good for the compressor)

- is there a problem with the outdoor equipment such as a bad control relay or control board

And yes the compressor/condenser unit should be level or close to level.

My Central Heating System Won't Turn Off

My central heat continuously run and does not shut off when it reach the temperature set on thermostat what could this be it - On 2018-10-27 by Gloria -

Reply by (mod) - What to do if heat pump won't shut off

Gloria

When your central heating won't turn off regardless of what you do at the thermostat, that's probably not a heat pump or compressor/condenser unit problem.

Instead, see the diagnostic steps at HEAT WON'T TURN OFF

 

Split AC takes too long to reach indoor temperature setting

Sometime my split ac take more than 2 hours to reach 24 degree temp sometime it achieved in a hour. However in each cycle compressor remain off for 2-3 minutes..

I suspect shutdown time between cycle is very less. Is it supposed to be 2-3 minutes only? - On 2020-05-08 by Raud

Reply by (mod) -

If the outdoor conditions and the buildings rate of heat loss or heat gain is more or less the same then I would agree that that much variation in cycle time for your heat pump suggests that something is wrong.

I would expect your service technician to check for a failing or sticking thermostatic expansion valve or a failing or sticking control relay.

Followup by Raud

Thank you for quick reply..

Unfortunately in my area no expert technician.. Outside temperature is 33..my room is on top floor.. Two window and two door cover by curtain.... In this case 2-3 minutes shutdown time is less right? Per hour how much minutes it should stay shutdown..

Reply by (mod) -

Raud

There's no "right" answer to the on-off cycle time for an AC or heat pump system as the big variables swing just too widely:

- outdoor temperature
- building heat gain or loss rate, including windows, air leaks, insulation, etc.
- efficiency of the whole system, including ductwork, fans, registers, etc.

Even a dirty filter will make a big difference in air flow and run times.

It's the wide cycle time variation that you cited that made me think the system needs repair.

Question: My A/C compressor just won't stop running

I recently noticed my AC condenser unit still running when the system inside shutoff by itself. and also, does the condenser unit have to be leveled. I notice the slap which holding the unit is slopping. Any suggestions? Thank you. - Rick

Reply:

A/C compressor/condenser won't stop running:

Rick usually when an A/C condenser unit won't stop running even though the inside equipment has shut off by itself my thinking divides into two investigations:

- is there a problem with the INDOOR unit such as a blower fan that won't start, an access door switch open, a condensate drain switch turning off the blower unit - these can leave the system calling for heat and the compressor running (though that's not good for the compressor)

- is there a problem with the outdoor equipment such as a bad control relay or control board