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Photograph of an old burned-out air conditioning compressor unit Burned-out A/C or Heat Pump Compressor Motor FAQs

Q&A on how to diagnose compressor burn-out

FAQs on air conditioner or heat pump compressor burn-out diagnosis & repair.

This air conditioning repair article series discusses the how to diagnose and replace a burned out air conditioner compressor.

Page top photo: even though this outdoor air conditioner compressor/condenser unit is obviously old and rusted, it was still working perfectly, more than 20 years into use. Age alone is not a reason to assume that the compressor in your air conditioner or heat pump will fail.

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Diagnose a Burned-Out Air Conditioning Compressor

AC Compressor © D Friedman at InspectApedia.com These questions and answers about diagnosing and fixing a burned-out compressor motor in an air conditioner or heat pump were posted originally at BURNED-OUT COMPRESSOR - be sure to see the advice given in that article.

Examples of Burning up, overheating or melting HVAC Compressor Wiring or Switches or Controls

Why did our air handler's power switch melt ?

What would cause the air handler power switch to melt? Last night, everything working fine...this morning, nothing that has to do with the heating/air will turn on, not even the thermostat on the wall...went to check attic, noticed a burnt plastic smell and saw the power switch was melted - outside fuse ok. Any ideas or suggestions? Thanks - On 2012-11-09 by Andrea

Reply by (mod) -

Andrea,

That sounds like perhaps a double hazard

A short circuit or bad connection at the switch and perhaps a fusenor circuit breaker that should have interrupted and turned off the circuit.

Check further for

A bad circuit breaker - see Federal Pacific Electric Stab lok info and also see aluminum wiring information both at InspectAPedia for examples.

I've been replacing burned wires at my compressor over and over - why do they keep burning up ?

My AC split unit stop working ,because the terminal wires connecting the compressor to the capacitor always burn this happen several times, and the remedy was to replaced the burned wires,please can you advise what the reason that keep the terminal wire burn, the compressor is newly installed, - On 2012-08-29 by Mohamed al lababidi

Reply (mod) -

Mohamed,

Watch out: you're risking an electrical or building fire.

If the terminal wires keep burning up I suspect that the problem is one of

- an overcurrent - high amps draw because a motor is seizing and needs replacement - most likely it's this problem

- bad electrical connections, possibly involving alumnum wiring or loose connectors

- improper electrical wiring - such as undersized wires for the length of run, or mis-placed connections

- abnormal voltages in the system or voltage surges

Central heat won't power on after breaker tripped.

I turned on our central heat and it wouldn't power on. I checked the inside breakers and found that the breaker had flipped off. I switched it back on and again it flipped off.

I then checked what I believe is the A/C Switch Fuse on the outside of the house (a double wide mobile home), the inside of this fuse box looks to be burnt black and has an odor of burnt wires.

I then proceeded to turn of ALL breakers to the unit.

My question is: Can we replace just the Switch Fuse or do we need to replace the entire system? - On 2012-12-14 by Nicki

Reply by (mod) -

Nick, we won't know what needs to be replaced without some investigation.

If a wire or control shorted out those can be repaired or replaced.

But if the short circuit or blown fuse occurred because of a seized compressor or motor, that too will need replacement.

A service tech will check the circuit, wiring, and components to sort out the problem.

Watch out: don't keep turning power back on. In a case like this you could risk an electrical fire.

 

Compressor won't run on my Trane XL 14i Model # 4TWX4036A1000A

I have a Trane XL 14i Model # 4TWX4036A1000A several days ago when I got back home noticed the inside Air Handler was running but the outside Condenser - Compressor was not running or cycling at All.

I checked the breaker and breaker for outside was tripped so I rest breaker and it tripped again within 2-3 seconds.

So I went outside opened up the unit to start troubleshooting the possible problem checking capacitor and contactor relay switch and looking for burnt or bad connection everything looked good.

I even replaced the 40amp breaker in main breaker panel and then verified I had power from main breaker panel to outside disconnect and all was proper voltage.

I checked condenser fan it it spun freely. I only have low voltage going to outside unit from air handler breaker as the air handler is still working, I bypassed the outside disconnect and wired directly to make sure there was not back connection in disconnect, reset breaker and tripped in seconds again.

Could the Condenser Fan cause this Problem even if Manually it spins freely as I have not removed as of yet to troubleshoot fan or is it looking like my compressor is burnt out or something else I could look into for possible cause of Problem.

I have had Hard Start on Unit for the last 6 months to help prolong life of Compressor and light on Control - Frost Board is on and Flashing per Normal 1 blink every 2-3 seconds no rapid blinking.

Any advice or Help would be Greatly Appreciated as I'm Hopling Compressor in not Burnt. - On 2018-01-18 by Dan

Reply by (mod) - Trane XL 14i compressor diagnostic discussion

More likely the compressor motor is seized. A tech would probably measure the current draw on that circuit to confirm the problem.

Other tricky failures that can mimic a burned out compressor (and also actually cause that failure) include a bad start/run capacitor or a compressor that can't start because it's pumping against abnormally high head pressure, perhaps because of a frozen TEV

Reply by Dan

Start - Run Capacitor is New as I keep several on Hand Always same as Contact Relay Switches and Fan Capacitors Also. Whats a Frozen TEV? where is it Located on Unit?

Reply by (mod) - signs of a bad TEV (Thermostatic Expansion Valve)

Dan

If the TEV (Thermostatic Expansion Valve) that regulates the flow of refrigerant from the compressor high side to the cooling coil (low side) jams or freezes it stops releasing refrigerant and the high side pressures climb and remain there.

Reply by Dan

Where is Location of TEV on my Trane Unit is there Way for me to Check the Valve. Also Would it be Common for Bad Condenser Fan to Possible Cause the Draw of Amperage to Trip Breaker in Seconds?

Reply by (mod) -

Dan you need an onsite service technician. The TEV, probably located in your air handler near the cooling coil, is not homeowner-serviceable. You can read about that device at https://inspectapedia.com/aircond/Thermostatic_Expansion_Valve.php

Reply by Dan

I Meant Quick Update on my Previous Comment several minutes Ago..

Quick I disabled the Compressor Wiring on Outside Unit and Turned Thermostat up to Call for Heat and the Condenser Fan is Working and DID Not Trip Breaker with Compressor Disabled So its Not the Condenser Fan.

I've had Heat as the Air Handler I'm guessing went into Emergency Heat Mode with Out Compressor or Outside Unit Functioning. Do you have any Other Advice that Could be the Problem besides the TEV or Compressor Being Burnt Out (Short to Ground)?

Reply by (mod) - the compressor that will draw high amps, moreso if frozen or failed.

Dan

Indeed it's the compressor that will draw high amps, moreso if frozen or failed.

Besides a stuck or frozen TEV or a failed compressor motor or bad start capacitor, sure there are other possible causes - not all of which fit in a brief e-text.

Your service tech might also look for a failed heating coil on the compressor motor or a bad control board that is not running the heat pump through a required defrost cycle.

Reply by Dan - what does "frozen" compressor unit mean?

By you Saying Frozen I'm Assuming you Meaning by that Seized Up or do you Mean 410 refrigerant froze up in Compressor and Valves?

Service Techs are Exactly Why my Unit is Messed Up High Prices and Shotty Repair Work and Parts Changers when the Parts were not even Bad most of the time.

Reply by (mod) - jammed thermostatic expansion valve can cause coil icing or freezing

A TEV can jam from dirt and debris or other contaminants including moisture that can actually freeze in a TEV. It's not a part you can change out yourself.


If the compressor in my LG air condtiioner unit failed why am I being asked to install a whole new unit?

If the compressor has burnt out on LG outside unit for ducted aircon why am I being asked to install a brand new ducted air con system instead of just replacing the compressor. - On 2018-01-15 by erica potter

Apparently two pipes were touch to heat up.

Reply by (mod)

I don't know, Erica, I Perhaps it is because there is a refrigerant type change.

For example R22 is now considered obsolete and changing the compressor might lead the installer to want to change the evaporator coil in the air handler inside


Compressor runs normally but suction line is hot

I had a compressor that would run and pressure seemed normal but the suction line is getting hot. It isn't a heat pump so no reversing valve.

Landscapers hit low voltage wire and I believe short cycled the compressor for two days before I got to it.

i checked and had continuity through all three common run and start. But I had power coming out of compressor at start terminal.

Therefore powering capacitor with 240 at herm terminal on capacitor.

Any ideas why this would happen. I've never seen this before On 2017-05-29 by Tony

Reply by (mod)

A short circuit or power surge could damage the HVAC equipment including a control relay odr board inside the unit.

A service tech will measure the current draw of the compressor motor and s/he'll measure the high side and low side pressures.

We need that diagnostic data.


Does low actual running load amps RLA mean that my compressor is damaged?

RLA for compressor is 13.44 I checked while running and it shows only 4.4 amp , is it compressor broken ? - On 2017-04-29 by Jank

Reply by (mod) -

Perhaps not, but I'm confused; you said the motor was drawing RLA but don't say if it was running or not.

I assumed (oops) that meant it was not running and that it was drawing higher than normal running amps.

Let's not mix up

LRA = lock-rotor-amps - you wouldn't see this amperage or current draw if a motor were running normally

RLA = running-load-amps - this is the normal current draw


Compressor draws LRA current then drops to zero

Compressor is pulling lock rotor amps,than the amps drop back to zero on the meter.Is the compressor locked up?. Everything else checks out. On 2017-04-29 by Darrell

Reply by (mod) -

Typically that's a seized motor or bearing, right?


Do we change out just the bad compressor motor or all of them?

if a air conditioning system has three compressors and one has a burn out ,would you change the one or would you change them all. - On 2017-01-24 by John

Reply by (mod)

I'd only change out the failed compressor motor unless there's something missing from your problem or diagnosis description


Replace the refrigerant lines when replacing a failed HVAC compressor?

Do you have to replace your copper pipe when your compressor burns out or can you use chemicals to clean out the copper piping? - On 2016-09-30 by Barry

Reply by (mod) -

Barry my OPINION is that - it depends - on how bad the refrigerant piping seems.

Typically when a compressor is replaced the installer places a burnout filter-drier or two on the system piping and might even return to replace them after some period, thus protecting the new compressor as well as the expansion valve from debris.


Sparks at the PTAC system when it's in heating moder

Trouble shooting a ptac system, put into heat mode sparks start,
Coolingbtu/HR 11700/11500
Heat 11300/11100
Electric heat watts 3400/2780
Electrical amp 15 - On 2016-09-28 by john

Reply by (mod) -

Watch out: Sounds like unsafe electrical wiring in the backup heating components. I'd be sure everything is turned OFF immediately to avoid a shock and fire hazard. Then review the wiring and connections and controls.


Outside compressor/condenser unit won't turn on

Replaced capacitor have power to fan, compressor and power coming in and out of contractor. Still outside unit not coming on. - On 2016-08-28 by Brian

Reply by (mod) -

If you've confirmed that electrical power is ON to the compressor/condenser and that the indoor unit is calling for the outdoor unit to run (in cooling or if a heat pump in heating mode) and the unit still isnn't turning on, the common problemd could be a bad relay or control board;

our tech will also check the current draw at the compressor to check for a burned-out or seized compressor motor.


Compressor stops and starts while fan keeps running

Had a new capacitor put in but compressor runs for a while then stops then after a while it starts back that's during the day fan still runs the whole time but at night it runs to its satisfied - On 2016-07-12 by Calvin jeter

Reply by (mod) -

Yes indeed, if a compressor or other electric motor is itself failing, such as due to a bad bearing or winding, replacing the capacitor won't repair that trouble.

 

Thank you to our readers for their generous comments

On 2016-05-20 by arich

Very nice article. thankyou its much helpful

On 2016-04-22 by dan h

Very helpful compressor diagnostic article, thanx

On 2011-08-11 by free

Good article, unbiased and well informed, thank you.

..

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