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Old 07-08-2020, 03:02 AM   #1
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HVAc trips when I turn on the AC. How to diagnose and repair?


A few days back, I found out that the fan of the HVAC system is running (fan inside is running and heating works fine) but the outside condenser unit is not running. The circuit breaker was tripped and whenever I switch on the circuit breaker, it trips again in 3-5 seconds. I changed the circuit breaker and it trips again.

I called a few HVAC guys and they suggested to change the compressor unit guessing that compressor is blown. They didnít even check it.

This is a 14 years old unit and uses R22 refrigerant. Changing the whole HVAC will cost me 7-8K.

Could anyone advise me how to check if the compressor is actually broken? And if it is, how much will it cost to change just the compressor?

Thank you !!
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Old 07-08-2020, 05:48 AM   #2
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Re: HVAc trips when I turn on the AC. How to diagnose and repair?


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...how much will it cost to change just the compressor?
A lot. The parts. The on job time.
The real cost is finding someone available to do it Mid Summer ...
and what you'll do to stay cool until then.

The lesson is to establish a relationship with trades people and contractors BEFORE something stops working.
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Old 07-08-2020, 06:06 AM   #3
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Re: HVAc trips when I turn on the AC. How to diagnose and repair?


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The lesson is to establish a relationship with trades people and contractors BEFORE something stops working.
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That's nearly impossible. 99% of the DIY'ers would have better success putting tooth paste back in the tube.
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Old 07-08-2020, 07:33 AM   #4
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Re: HVAc trips when I turn on the AC. How to diagnose and repair?


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Originally Posted by SeniorSitizen6218115
That's nearly impossible.
Don't be absurd. It's entirely possible and advisable.
Every homeowner should have that list of names.

Quote:
99% of the DIY'ers...
...might aspire to a broad base of technical competencies
but rather few will ever approach it.
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Old 07-08-2020, 07:45 AM   #5
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Re: HVAc trips when I turn on the AC. How to diagnose and repair?


Phone more companies until one agrees to come out and check it.

Play dumb and don't tell them the age. Just say you don't know and cannot find the model # sticker. Eventually you will get someone to come out

You may have a weak capacitor but you may also have a stalled and seized up compressor. At that age it is not worth replacing the compressor as that may run you $2000 in cost or more.

Ask your friends, neighbors, co-workers if they know someone reputable.
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Old 07-08-2020, 07:47 AM   #6
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Re: HVAc trips when I turn on the AC. How to diagnose and repair?


Check and see if the windings of the compressor are shorted to ground with your meter.
Don’t call companies expecting them to be a free technical service line. Or you’ll get silly answers like you’ve gotten.
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Old 07-08-2020, 08:41 AM   #7
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Re: HVAc trips when I turn on the AC. How to diagnose and repair?


It likely has a short and it may not be in the compressor.

No need to replace unless the compressor has failed.
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Old 07-08-2020, 12:55 PM   #8
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Re: HVAc trips when I turn on the AC. How to diagnose and repair?


That doesn't sound like a failed capacitor. It would likely mean there is a dead short somewhere since the breaker trips so soon.

Even so, check the condenser to see if it is bulged up on top where the terminals are. If not and you have no meter to test it with, read on.

If you're a handy DIY'er, disconnect the compressor wires from the contactor and try resetting the breaker. If it stays on this time, you likely have a bad compressor. If it still trips, disconnect the fan wires from the breaker and repeat the test. If it stays on, check the fan wiring and if no problem found, the fan motor is bad. If it still trips, you're lucky, it's a short somewhere and you or someone else can find and fix it without it costing an arm/leg.

Don't even consider replacing the compressor if it's bad. It's time for a new system... but normally it need not cost over half what you stated.
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Old 07-09-2020, 09:59 AM   #9
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Re: HVAc trips when I turn on the AC. How to diagnose and repair?


surferdude2 got it right. It's a process of elimination. When the breaker trips that fast, you have a dead short to ground somewhere. It could be the capacitor, it could be the condenser fan, it could even be the crank case heater (if it has one) and of course it could be the compressor. But if it is the compressor, don't be foolish and replace it. Invest in a new unit.
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Old 07-09-2020, 06:10 PM   #10
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Re: HVAc trips when I turn on the AC. How to diagnose and repair?


I should have asked the OP if he had a multimeter. Dead shorts are easily found with an ohmmeter and less traumatic on things.

Oh well, I've done it both ways and never destroyed anything.

Sometimes when using that "poor people have poor ways" method the magic smoke comes out of something and makes it an easy find.

Perhaps he'll come back with some good news and it was a dead mouse spread eagled on the capacitor terminals to ground.
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Old 07-11-2020, 01:43 PM   #11
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Re: HVAc trips when I turn on the AC. How to diagnose and repair?


Turn the breaker off. Get a multimeter that tests for power.

Unscrew panel. use multimeter to make sure power is truly off.

Once you confirm power is actually off, Use a screw driver to short the prongs on top of the capacitor. It looks like a big cylinder battery. There's youtube videos how to do this.

Once that is done, it is safe to begin looking around. Take some pictures. Inspect wires for corrosion or failed insulation/shielding. Use some electrical contact cleaner to spray down anything that looks like corrosion build-up.

Or take a bunch of pictures of all the wiring and post them here.

It sounds like something on the high voltage side is shorting, which probably means more expensive parts. Focus on the contactor switch. It's a big block with a lot of wires connecting to it. low voltage wires on each side, high voltage wires on top and bottom.

I pulled the panel off mine once and saw what was left of a fried lizard. LOL Maybe you'll see something obvious.
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