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I had an AC unit stop working and the tech that arrived placed a temporary hold on the contactor for the inside unit until we could get the parts. After a couple of days, the AC went out again and when they returned, they found the compressor in the outside unit had stopped working and now they're saying both the compressor and air handler have to be replaced. Is it possible that the temporary hold on the contactor could have caused the compressor to fail?

Thanks!

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    "until we could get the parts." wtf. You drive to a store, buy one, then up-charge the crap out of them for the trouble. You don't clamp down a contactor with anything other than you holding a screwdriver to see if the unit works, ever. Did you agree to: hey I can make this work over the weekend for you (not that I should), or I can charge you $800 to go get the part (because you live in Alaska?) and do it right, today. - Thought this said place a hold on a contracter - if you 'agreed' then no. If it was of their own volition, yes. non-workmanlike manner doesn't get the benefit of doubt
    – Mazura
    Commented Jun 8, 2023 at 2:22
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    @Concerned Homeowner - Do you have any more details of what the tech meant by "temporary hold ... for the inside unit" or what effect it had? (Understanding that the tech may not have been entirely clear in the first place.) Like, the contactor for what? Commonly the only contactor is part of the outside unit.
    – Steve I
    Commented Jun 8, 2023 at 13:21
  • @Mazura Sometimes it just isn't practical to get the part right away. Problem happens on a Friday afternoon and parts places aren't open until Monday morning. Even worse if there is a major holiday on Monday. Common stuff can be bought at big box stores, but if a control board or sensor needs replacement that isn't an option. That being said, it is on the technician to know when you can safely bypass something and when you can't. I once had my tech. out on December 25 (he didn't mind, he was sitting around the house with nothing to do, easy money) but he couldn't get the part. He told me Commented Jun 8, 2023 at 14:27
  • what to get (ignitor for gas furnace) and my brother who was in the parts business (but didn't have it himself) called in to a parts place the next morning and I picked it up on his account and installed it myself. But not all parts are that easy, sometimes the wait is longer, not everyone can install things themselves (even I have my limits, I won't touch gas piping or refrigerant), etc. Commented Jun 8, 2023 at 14:30

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I am not 100% sure what "hold" on a contactor means. But my suspicion is that it means somehow forcing a contactor to be closed when it might not otherwise be closed - i.e., to constantly run some piece of equipment instead of it depending on a thermostat or other sensors. That could be done by physically forcing the contactor closed or by bypassing that part of the circuit with a wire.

Doing something like that is not always bad. For example, several years ago the fan in my air handler stopped running. My HVAC technician was able to determine that the problem was with the circuit turning the fan on, and he was able to temporarily rewire things so that the fan stayed on all the time (simply setting the thermostat to Fan=On wasn't enough to do that - there was something else wrong) and the rest of the furnace cycled appropriately, so I had heat for the day until he could come back with the parts to do a permanent repair.

However, with air conditioning (and heat pumps in general, and often other types of appliances), there can be additional safeguards - timers (to make sure a compressor doesn't cycle too quickly), pressure switches, temperature sensors, etc. - and bypassing a contactor or forcing a contactor to always be closed (=on/running) will bypass these extra protective devices. See this Technology Connections video for a description of how this works.

So what may have happened is that one part was failing and causing a safety switch, perhaps detecting high pressure or temperature, to stop the A/C from running. By forcing the unit to run anyway, instead of the problem causing a safety switch to stop the system before too much damage was done, the system kept running until it essentially destroyed itself.

Is that definitely what happened? No. It is possible that the system was so close to total failure that it would have failed anyway once the initial problem was resolved. Or the problems may have been totally unrelated. But it certainly seems likely that overriding safety devices could have caused a cascade of problems leading to total failure of the unit.

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    Agreeing with manassekatz: Summarizing his post: The total hack job of bypassing the contactor is terrible idea. that would mean the compressor is running all the time. As Manassekatz said: ". By forcing the unit to run anyway, instead of the problem causing a safety switch to stop the system before too much damage was done, the system kept running until it essentially destroyed itself." The contactor is controlled by electronics and sensors that probably sensed something wrong and wouldn't turn on the compressor. And now he wants $$$ to replace the system he broke. Sue him. Commented Jun 8, 2023 at 14:17
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This is an assumption and a SWAG. However bypassing the contactor and forcing the compressor to run continuously bypassed all of the Safety and control devices on the unit. In my opinion that is an poor hack of a solution and probably caused the compressor to fail. I am assuming the winding in the compressor failed contaminating the evaporator (inside coil) causing it to need replacing. I highly recommend you get another company to replace the unit and place this company on your do not use list.

There was a reason the contactor did not work in the first place.

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