Seized air conditioner or heat pump compressor motor diagnostic questions & answers.

This air conditioning repair article series discusses the Diagnosing Tight or Seized Air Conditioning Compressors and how to re-start a tight air conditioning compressor. Advice for measuring amps or current draw to check for a seized or tight or failing A/C or heat pump compressor motor

Tight or Seized Air Conditioning / Heat Pump or Refrigeration Compressor FAQs

These questions and answers about the causes and diagnosis of tight or seized HVACR compressor motors were posted originally

at TIGHT or SEIZED AC COMPRESSORS - be sure to check out the diagnostic suggestions on that page.

 

What to check if the AC compressor is buzzing

Don,

There is a fairly rare failure that you can check. If the compressor unit is humming or buzzing, which sometimes can be so loud that it sounds dangerous, pull the service disconnect (or shut of the main breaker) and check to see if an insect is smashed anywhere in the compressor contactor (relay).

When spraying the unit it may have caused an insect to look for a new home and sometimes they crawl in and get smashed when the contactor closes.

If it gets smashed by the armature it usually just makes noise but if it gets smashed by the contacts it can cause both noise and failure to apply power to the compressor.

It is also possible that a smashed insect can cause arcing which in turn can make a little smoke and a bad smell and cause the contactor to fail.

This problem usually only happens with insect invasions, like spiders and crickets, but I've seen it in very hot summers after someone waters a flower bed next to the compressor unit.

Whenever I install units I seal all holes in the electrical area with a dab of RTV silicone so insects can't get in. That also helps keep water out. On 2018-06-23 by Perkins -

- by (mod) -

Perkins

Thank you for the helpful comment. We'll be sure to keep your tip in the HVAC repair suggestions.

Heat pump is buzzing on startup

Have a 12+ year old Trane 3T heat pump. Charged last summer for the first time. It ran well this summer and so far during this fall, but it makes a 1 second buzzing sound, not a rattle, occasionally on startup. Other times its snap and go, with no unusual noises.

Capacitor was low value, so I changed it and the contactor

. It still runs well and I think the noise is less frequent, certainly not on every startup. Electronics is my forte, not refrigeration but I am comfortable making tests. Any suggestions?
(When it was recharged last summer the refrigerant was not weighed.) On 2018-10-30 by Len -

by (mod) -

Please take a look in the article index at the end of this page and you'll find a series of articles on HVAC noises including sources of buzzing.

Take a look at that and let me know what you think.

Should I try a hard start capacitor on my stuck compressor motor?

I have a 3 year old American Standard -- still under warranty for parts -- and I believe the compressor is stuck.

This theory is based on a lot of research and testing. The wiring diagram shows an optional start kit accessory, including a capacitor switching relay and a starting capacitor. Should I try installing such a device? On 2020-06-09 by Moe

- by (mod) -

Sure, since that's an inexpensive try that can sometimes get a bit more life out of a failing HVACR compressor motor, but from what you have said i suspect the motor is shot.

Window A/C unit stopped working after I washed it with water

I have a 220 window unit that hasn’t been running in about 6 months I cleaned the unit with just water and waited until the next day to turn it on it ran great for about 20 min. And shut off and when it came back on the unit started humming and the fan would not come back on what could have happened ? On 2018-02-26 by Don Gates

- by (mod) -

Don,

I'm only speculating, but it's possible that the water that you sprayed got into the unit and either wet and shorted an electrical component such as a start capacitor or relay, or less likely got into a motor bearing such as a fan shaft bearing causing it to seize.

Watch out: I would leave it turned off

The compressor motor stopped working during a service call

We just had an a/c guy come out and one minute the compressor worked, he did something inside by the compressor (when I asked him later, he said he was testing continuity) but when he restarted it, the compressor wouldn't start.

He tested the amp draw at that point and said that the compressor finally quit as it wasn't drawing any current.

Is this possible? Or is he "scamming" me?

We originally called him because the a/c has been cooling the house less and less over the last week and a half. On 2012-07-25 by Tim

- by (mod) -

Tim:

If the compressor was not starting before the A/C technician came by and he tested the compressor motor for an internal short or open winding, that's pretty sharp and quick diangosis.

I understand the frustration at both surprise and being faced with a big bill, but I'd need something more suspicious before I'd insult the tech with a scam charge.

Certainly you have the option of asking for a second opinion from a different company or technician. Indeed there are plenty of reasons that a compressor motor won't start. And I'm not sure how "cooling less and less" over time maps to a seized compressor.

It may have been having trouble starting, but finally starting up?

How do we wiggle an A/C comprssor motor to try to un-jam it??

How do you move a air conditioner compressor motor back and forth to try to unstick it? On 2012-06-02 by Jerry

- by (mod) - sorry that's not really a good idea but ...

Jerry, presuming you're talking about the compressor motor itself, if it has jammed, most service techs will assert that the unit is shot and needs replacement.

The compressor motor in a typical residential or light commercial air conditioner, heat pump or refrigeration equipment is in a hermetically sealed metal container. You cannot physically "wiggle it" to get it un-stuck, and even if you could, the fact that it jammed means it's at or near the end of its useful life.

There are two things a technician might try though:

1. A hard start capacitor can give the motor an extra shove to see if it will work for at while longer.
2. Voltage surge: Sometimes a jammed electric motor can be got going by an expert using a surge of current or voltage
   
   Watch out: this is not something I'd recommend for any homeowner ecause it is dangerous (risk is fire or shock) and because once a compressor motor has really frozen, even if you got it spinning again it's damaged internally and is unreliable.
   
   

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Continue reading at TIGHT or SEIZED AC COMPRESSORS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see TIGHT or SEIZED AC COMPRESSORS-FAQs, diagnostic questions & answers posted originally at this page.

Or see these

Recommended Articles

• COMPRESSOR / CONDENSER REPAIR - home
• BURNED-OUT COMPRESSOR
• CAPACITORS for HARD STARTING MOTORS
• COMPRESSOR / CONDENSER DIAGNOSTICS
• COMPRESSOR CONDENSER NOISES
• COMPRESSOR MOTOR REPLACEMENT
• CONTACTOR RELAY DIAGNOSIS & REPAIR
• HARD STARTING COMPRESSOR MOTORS
• TIGHT or SEIZED AC COMPRESSORS

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