Q&A on air conditioner or heat pump compressor motor replacement requirements & procedures.

This air conditioning repair article series describes the basic steps involved in replacing a burned out air conditioner compressor.

FAQs about Air Conditioner / Heat Pump Compressor Replacement

These questions & answers about the process of replacing the compressor motor in a heat pump or air conditioner unit were posted originally

at COMPRESSOR MOTOR REPLACEMENT - check the details given there.

Compressor failed after start capacitor replaced - blame the capacitor?

We recently had our "Start capacitor" replaced on a 9 year old Trane HVAC. 3 days later, unit stopped cooling and technican says "compressor is shorted to the ground".

When asked if the start capacitor replacment could have created any issue with the compressor shortage, he said "absolutely not".

That seems inconsistent.

If the starter capacitor is a "energy booster" to the compressor, how could it be completely unrelated?

So my question is, could/is it possible for a new start capacitor install create an "energy event' which would cause the compressor to short out?

The tech said there was no way they could be related technically, Just need an HVAC genius to provide their insight.

I would appreciate it. I'm looking at 2400 to replace compressor or 7K for new unit. 2016-08-16 by Anonymous

Reply:

Well absolutely is a pretty strong word from a nervous technician.

A wiring error or missing the real problem could either be at fault.

Often when a compressor is hard to start it's because it's seizing and at end of life - could have been damaged by a variety of problems. The tech sticks on a hard-start cap because that's dirt cheap to try and might keep the old boy cooling a bit longer.

But it's no surprise if the compressor itself is shot and now needs replacement. It was probably shot before the cap was installed.

And yeah, though it's IMO VERY unlikely, an enormously over-sized capacitor might damage an electric motor to which it was wired.

A sharp tech might have confirmed that the compressor is really shot by at least measuring the current draw at the motor.

 

Compressor motor problem: outside heat pump unit voltage increases from 246 volts to 298 volts when shutting down

My outside heat pump unit voltage increases from 246 volts to 298 volts when shutting down.

Makes loud noise as it finally winds down. The tech says its something in the compressor, something like "ribbons" but was another word.

Will cost $1300 to replace compressor, part under warranty, just paying labor. Any other options? 2018-01-14 by Mark

Moderator reply:

Mark,

I don't know what ribbons meant, and I would be very grateful if you could get some more detailed explanation from your contractor and then pass that on to us for understanding and research.

I am also not familiar with a compressor-motor defect that would increase the voltage level at a heat pump.

However, abnormally high voltage (or voltage surges) delivered from your electrical power company's electrical grid can damage an A/C compressor as well as other electrical devices and equipment.

• Shaffer, John W. "Air conditioner response to transmission faults." IEEE Transactions on Power Systems 12, no. 2 (1997): 614-621.
• De Leon, JA Diaz, and Carson W. Taylor. "Understanding and solving short-term voltage stability problems." In Power Engineering Society Summer Meeting, 2002 IEEE, vol. 2, pp. 745-752. IEEE, 2002.
• Breuker, Mark S., and James E. Braun. "Common faults and their impacts for rooftop air conditioners." HVAC&R Research 4, no. 3 (1998): 303-318.

Typically a failing heat pump motor draws abnormally high current (measured in AMPS) not voltage (measured in VOLTS). Those terms are explained

at DEFINITIONS of ELECTRICAL TERMS

When a compressor motor is drawing abnormally high current (amps) that's often a sign of a failing motor - bearings are seizing making it difficult for the motor to spin. Sometimes a service tech might try installing a hard start motor capacitor as a very inexpensive step to see if she can get a bit more life out of the compressor motor.

See HARD STARTING COMPRESSOR MOTORS

and see
CAPACITORS for HARD STARTING MOTORS

Follow up:

I will call them tomorrow and find out what exactly. They did recommend I have the electric company come out which I did and they said it is receiving 246 volts which is within parameters. But the company I'm having fix it says on shutting down the voltage increases.
Thanks so much for responding!
Mark

Reply:

Ok, keep me posted. What you learn will help other readers.

Follow up:

They changed the board but it still doing the same thing. They are going to replace the compressor next week. The system is running on emergency heat so the whole thing doesn't burn out in the meantime.They have never seen this problem before which is a little surprising since it's a company with 5 locations, not a mom & pop business.

They are here now to fix it. What they are going to try first is replace the Board since it's easier/cheaper. They say the stored energy in the capacitor is discharging into the compressor and the fan on shut down. We'll see...

Reply: abnormally high voltage damaging the compressor/condenser unit?

Mark

Thanks for the updates. All of this sounds strange to me but probably we're seeing a communications gap between the technicians and the rest of us. There sounds like a confusion between volts and amps, or at the least, I'm unclear how a control board OR a bad compressor would change the VOLTAGE readings.

Central air conditioner compressors run at 120VAC or more-often 220 or 240 VAC nominal voltage.
Some units will specify an acceptable range such as 208-230VAC or, depending on your country and electrical service, up to 250VAC.

I agree that 246VAC is within acceptable limits for the supply voltage to many AC condenser units.

The AC circuit should be dedicated - it should not be also supporting other electrical equipment.

If the supply voltage (from the electrical utility) is exceeding what the equipment can handle that can damage the equipment. But you'd want to do more than just fix the equipment; you'd probably want surge protection and voltage conditioning equipment to protect the repaired compressor/condenser unit from new damage.

A typical voltage stabilizer will handle voltages ranging from 170-270VAC and will keep that voltage in the range needed by your equipment.

Research:

• Ortega, JM Maza, M. Burgos Payán, JM Romero Gordón, and M. Pinilla Rodríguez. "Supply Voltage Effects on the Operation of Residential Air Conditioning Appliances: Theoretical Analysis."

What's a reasonable price to repalce a 3 Ton Goodman Compressor?

I am a claims adjuster. Writing an estimate to replace a 3 ton compressor (Goodman).

Got an estimate for $1865.87 which seems high. I am putting in to remove and replace the compressor, recharge refrigerant, anything else needed? Does this price seem high? On 2011-11-20 by Jeremy Emert -

by (mod) - compresor replacement comment from insurance adjuster

Jeremy the compressor replacement procedure involves some extra time and care for the replacement to be successful, including evacuating and cleaning the existing refrigerant system, possible replacement of other parts that may have been damaged during the burn-up such as refrigerant metering devices, and installation, perhaps even more than once, of filter/driers on the refrigerant piping.

In sum, in my OPINION, the cost to replace a burned-out compressor with one of equal capacity, is probably a bit higher than the original installation cost - extra work is involved.

Currently (February 2025) a complete 3-ton Goodman Condenser unit heat pump + air handler unit sells for about $4300. before installation cost.

New compressor, refrigerant lines seem blocked

We just had a compressor failure on a 5 ton r-22 Ac unite only. The compressor was replaced by the tech lines purged and checked and recharged. The system quickly goes into Vacuum 20 plus inches Hg. Showing a blockage somewhere.

I watched the tech take the orfice valve apart and check it again and purge the lines and revacuum.....still going into Vacuum on the low side.

This man is an older tech who has been in the Ac business for 50 years and he seem to be puzzled. Oh, The tech said that on inspection of the orfice both times it was clear and their was no contamination. Any Help? On 2011-08-06 by Joe

by (mod) -

Joe I'm reluctant to second guess the tech that was on the scene, but indeed it does sound as if there is a blockage. Other blockages occur besides at the TEV, such as at a dryer in the refrigerant piping, and on occasion a blocked coil.

by Joe- Blocked condenser coil at the compressor?

Talked with the tech again today and he now thinks the blockage may be in the condensor coil right after the compressor. The plan is to disconnect the compressor back flush the condensor coil with high pressure nitrogen and see if the blockage can be discharged.

This system does not have a TEV valve just a plain old orfice. It also does not have a dryer anywhere in the system. I also looked at the lines from the condensor to the evaporator and the do not appear to have any damage anywhere.

( lines set runs from the evaporator in the ceiling to the condensor). The orginal compressor was locked up tight and the tech said he did not see any contamination in the lines. The high side pressure was running around 150 psig and low 22 in hg vacuum.

Thanks for your help and will let you know how this one turns out. Oh, I am an automotive tech and do have some refrigation training however I was just watching and assisting the Tech on this job since he seemed to be having some trouble.

by (mod) -

Joe the "plain old orifice" is also referred to as a capillary tube or cap tube - easily blocked by debris or even a slug of refrigerant oil. Interesting to read there is no dryer on the system.

SOP in many areas is that whenever we cut open refrigerant piping - say to replace a compressor unit - we install a filter/dryer at that time. In fact if a compressor has burned up and is being replaced we install a special burnout filter/dryer to try to catch the debris that the burn-up puts into the piping system.

See REFRIGERANT DRIERS & FILTERS under "REFRIGERANTS" in the ARTICLE INDEX found near the end of this page.

Voltas Plus 1.5 Ton Window A/C compressor not working

I have the voltas plus 1.5 ton window ac the unit turns on and the fan works but I can't get the compressor to kick on. I have tired turning the power on and off. Unplugging the unit. Changing modes from "cool" to "fan" and back to "cool". Any suggestion? (July 5, 2014) karan

Reply:

Karan

for diagnostics to address an air conditioner that won't start, please see

AIR CONDITIONER WON'T START

I suspect a bad control or a seized compressor motor

 

Question: replacement compressor motor now won't work

Compressor on a spilit system air conditioning unit was replaced about a year ago, now the newer compressor wont operate.

Checked the freon and blacken in color, what is the correct way to clean the system before installation of another compressor? (Oct 10, 2014) RJ said:

Reply:

The system is emptied of refrigerant, a vacuum pulled for at least 24 hours, and a special burnout filter drier is installed along with the new compressor motor.

...

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

Or see these

Recommended Articles

• BURNED-OUT COMPRESSOR
• CAPACITORS for HARD STARTING MOTORS
• COMPRESSOR CONDENSER - home
• DIAGNOSTIC GUIDE A/C or HEAT PUMP
• DIAGNOSTIC DETAILS A/C or HEAT PUMP
• HARD STARTING COMPRESSOR MOTORS
• TIGHT or SEIZED AC COMPRESSORS

Suggested citation for this web page

COMPRESSOR MOTOR REPLACEMENT 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

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