A/C & Heat Pump Compressor/Condenser Repair FAQs

Q&A: condenser unit won't start, won't stop & other snafus

Compressor/Condenser Unit Not Starting FAQs

Outdoor Compressor won't start

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? (July 13, 2014) Anonymous 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? (Aug 2, 2014) Lou said:

Reply:

Lou

Check for a bad start relay.

Then see AIR CONDITIONER WON'T START

What keeps a heat pump from kicking on

What keeps a heat pump from kicking on? by Steven Hagewood

by (mod) - What keeps a heat pump from kicking on

That sounds like a control board or switch problem.

• 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.

by Steven- cleaning fixed the control

I cleaned it and it works fine now

Delay in when the compressor starts and cool air begins

I'm no HVAC expert but i understand how it all works. My problem is that the indoor blower comes on, the outdoor fan comes on, but the compressor seems to take a while to come on, sometimes up to 10 minutes, meanwhile its blowing non cold air around the house.

I go outside next to the compressor, when it comes on i hear the fan but not the compressor (no buzzing sound), but it does come on later and then the freon pipe gets cold and I'm all good.

I am in Miami and it is getting pretty hot here this summer, is this delay normal ? or is it a prelude to a more major issue ?

Thanks. 2018-08-08 by Paul

Reply: normal delay in outdoor compressor motor start-up?

Paul,

The delay you described could be normal. For example in my office where we use a Sanyo split system air conditioner, the indoor blower unit may keep running at low speed but the outdoor compressor will turn on and off depending on when the control board (with its own computer) figures that it's needed. That's an energy-saving feature.

But IF your AC blower is delivering warm air AND the room temperature is still above the thermostat setting, then yeah something's wrong, perhaps with a sensor or control relay on the unit. That may not be a major repair cost ( a new compressor would be a major cost).

IF you hear the compressor humming but not starting, that's not very good and means there's a more serious problem. Call your service tech. Let me know what you're told.

Compressor won't start until it has cooled down

When my outdoor compressor/condenser unit is cold it will start and run.

But 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? Wayne

Reply:

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

See

COMPRESSOR / CONDENSER COOL with AIR or WATER? FAQs - spray or immerse in water as a diagnostic or to improve efficiency

 

A/C compressor not turning on

The outside unit of the heat pump is icing up on the compressor and the compressor won't start. - Steve 8/7/11

In the indoor air handler the fan in my house goes on but my outdoor compressor unit does not. All the electric seems to be fine . Could it be my thermostat? - Sam 8/7/11

the accu very heat,although it is new gen. clean,2Tr LS-60psi & HS-100psi, - Anon 8/6/11

Reply:

Steve: icing at the compressor/condenser sounds like a refrigerant charger or refrigerant metering problem.

Sam: if your thermostat turns on the air handler but the compressor/condenser does not run, the problem is not the thermostat. Check out the diagnostic suggestiosn beginning at LOST COOLING CAPACITY (link at the ARTICLE INDEX the bottom of this article )

Anon: those pressures look kind of low, no? What does your HVAC tech say about normal for that system?

 

Condenser unit won't run after I cleaned off wet leaves

I took the top off my central air unit to wipe the wet leaves, & dirt out i put the top back on

i tried to be careful & now it has power but fan doesnt turn did i maybe bump a wire plz help me its so hot i dont h $ right now is there a reset button On 2017-06-13 by Anonymous

by (mod) - bumped a plug-type wiring connector and loosened it.

Anon

Most-likely you bumped a plug-type wiring connector and loosened it.

With power OFF to the unit, you can remove the cover and look for wires to the fan motor - follow those to see if there's a disconnection.

Assuming that the fan and condenser/compressor unit was working last time it was used, and that you had power off to do your cleanup, it's not likely that there is a fan reset button problem; the reset on a fan motor trips if a motor overheats; not all fans have such a button as some thermal overload resets are internal and will re-set themselves automagically after the motor cools down.

Condenser Unit Won't Stop, FAQs

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

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.

Other Condenser Unit FAQs

Will a mini split work on both 60Hz and 50 Hz power?

Would 220/50hz mini split unit work with US 220/60hz apartment?

What is to check, its 50hz not 50/60hz. Somebody told me it will not give me as much cool as it suppose to be.

Is it correct? I thought 60hz will make compressor to work faster, not slower? On 2017-05-06 by Mark -

Reply by (mod)

Check the manual and data tag to see the voltages for which your unit is rated. Often, yes, the voltage and cycle rate have a small effect on motor operation and efficiency.

Chipped reed valve cannot be repaired or replaced, so I require a whole new condenser

I was told a chipped reed valve cannot br repaired or replaced, so I require a whole new condenser. I've been unable to find information here about repair or replacement of reed valves. Please help me find the answer. - On 2016-05-08 by Peg -

Reply by (mod) - a sealed HVAC compressor motor is not repairable - it gets replaced

Peg,

What you were told is correct. A/C or heat pump compressor motors are a hermetically sealed unit: the motor and components are in a "can".

It is not possible to repair parts inside the unit. The repair is to replace the compressor motor; there are perhaps other reasons why your repair person wants to replace the entire compressor/condenser unit instead.

Blue gummy substance used to patch refrigerant leak!

We had our air handler replaced just about 1 month ago but not the out side unit! I was surprised because the unit out side and in were put in when the house was bui!t in 1997.

There was a freon leak in the unit inside.

I was told there was no leak outside but there is a blue gummy substance where it looks as if the tried to patch a leak!

So why would someone not deem the whole system shot and replace the whole unit! Cause I seat here now with a non working unit again after dumping more than 800.00 into the unit on the inside and no freon in the unit yet again! On 2015-06-10 by Donna -

Reply by (mod) - if A/C refrigerant leak patch is not successful

Donna I can't diagnose this from just your e-text; no one would, however, be able to patch a refrigerant leak with an external black gummy substance that I know of.

More likely that's something else, perhaps sealing an opening where tubing passes or replacing damaged refrigerant tubing insulation.

IF your unit has lost refrigerant, indeed there is a leak to find and fix. Do not waste money by repeated re-charges of refrigerant (nor do we want to keep dumping refrigerant into the environment).

Surely the new work was warranted, right?

Building owner doesn't want A/C compressors installed anywhere that they can be seen

I am an architect with limited technical knowledge of the mechanics of A/Cs but based on past experience I have noted that compressors are normally located externally to provide air circulation around them or else they'll pack up.

On one of the projects one of my colleague is currently involved with is where the building owner has specifically stated that he does not want anything including compressors or satellite dishes installed externally where they are visible. the mechanical engineer has instructed the sub-contractor to install these in a stair well.

My opinion is that this is not the correct location as the stair-well will heat up due to discharge from the compressors - which means we'd need to provide mechanical extract! but more importantly due to lack of fresh air the compressors will within a short time pack up and the A/Cs will not function.

The mech. engineer who disagrees with these observations! Please advise if I am incorrect in my observations and what are the remedies.

Please also note contractually we've done the paperwork in informing the mech. engineer that the instructions are incorrect and any malfunction of the system as a result will be his responsibility - so that has been taken care of but what I'd like to know is whether we can go around this problem by introducing ducts or substituting outdoor compressors with indoor units which are more cost effective On 2013-01-18 by JR -

Reply by (mod)

In many buildings it's possible to install the compressor/condenser unit on the rooftop where it's not visible - but be sure to review noise control and noise issues for building occupants too.

Watch out: Avoid fencing in the condenser units and avoid locating them where they can't be readily inspected or serviced. Otherwise the future maintenance and repair costs may be quite high and may be a source of new complaints.