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Old 28-08-2013, 22:44   #31
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Re: Has Anyone Repaired an AC Unit?

If you even touch a schrader valve, check for leaks afterwards. Those things are notorious for leaking after they have been disturbed.

Also, low system pressure is as likely to cause a safety device to shut down a compressor as high system pressure is.

Knowingly venting refrigerant to the atmosphere is a cardinal sin in the refrigeration industry. You are required by law to recover the old refrigerant with proper equipment. That is the big reason why they now require licenses to purchase some types of refrigerants. They are trying to prevent DIY people without recovery equipment from venting old systems before recharging.
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Old 29-08-2013, 01:44   #32
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Re: Has Anyone Repaired an AC Unit?

If it runs for 15 minutes or so before it shuts down it sounds like the compressor is over heating rather than it being a mechanical problem particularly if it's not rattling or knocking.

If it has been running OK for a considerable period without problems and has just started misbehaving it is more likely a problem with the water cooling to the condenser or it is out of gas and has sucked in air which loads up the compressor because it cannot be liquified. If this is the case it only needs vacuuming and recharging and a check for leaks.

Boat refrigeration work is not too difficult to learn and does not require an extensive or expensive tool kit. If you are going to remote places and are dependent on the refrigerator it is well worth learning the basics.
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Old 29-08-2013, 02:59   #33
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Re: Has Anyone Repaired an AC Unit?

I had the AC in a car go down a few years ago. The main garage were talking new compressor and other parts plus unable to do anything for 2 weeks due to their supply chain. Cost made my bank manager wince.

I got a domestic refridgeration engineer take a quick look. He replaced the theremometer bit and regassed, and it worked better than it had ever done before. (it was also very quick and cheap)
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Old 29-08-2013, 05:56   #34
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Originally Posted by pbiJim View Post
Also, low system pressure is as likely to cause a safety device to shut down a compressor as high system pressure is.
Low system pressure can trip a safety device inside the unit if one is installed but it will not trip the circuit breaker which is what the OP reported. High system pressure can cause a circuit breaker trip. I see this a lot when DIYers add gas thinking this will improve the cooling when the real problem is low water flow. After the low water flow is fixed by cleaning the strainer the high gas pressure still causes problems. It also happens when a boat moves from cold water to warm water. The pressure rises and stalls the compressor.
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Old 29-08-2013, 06:09   #35
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Re: Has Anyone Repaired an AC Unit?

I made the comment about low pressure shutting down the compressor in response to another person suggesting that he should vent a little gas & see if things work. I was not trying to suggest that he now has a low gas supply.

The actual refrigerant charge needs to be pretty darn accurate for the system to work with good efficiency. Either too much or too little will reduce cooling capacity. Being off by as little as 10% can make a noticeable difference. The proper refrigerant charge can be measured in one of two ways. Either you weigh the charge when you install it in an empty system at dead vacuum, or you measure high side & low side pressure at the same time at a known ambient temperature & compare the pressures to a known chart. The pressures vary quite a bit as ambient temperature changes.
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Old 29-08-2013, 06:54   #36
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Re: Has Anyone Repaired an AC Unit?

I repaired ours at the beginning of the season, and it always seems to have an issue, probably because we rarely use it.

I've given up and now just open up all the windows and wear less clothing.
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