AC diagnosing help

AC diagnosing help

Postby AstroOafAdventurer [OP] » September 16th 2020, 3:50am

So with summer winding down I'm going to have a look at my AC.
The issue is most likely due to 0 R134 but I'm going to follow the FSM steps.
It may have a leak, hasn't been used in years and I found another thread on here mentioning seals going bad after non use.
I'm not sure where the low pressure switch is to test the compressor, and if that turns out fine, what should I look at for leaks?
When I got it I put two 11oz cans in and seemed to go out as fast as I put it in as the gauge dropped right back to 0 fairly quickly and was confirmed by a service station it had nothing.
Thanks!
Thor
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Re: AC diagnosing help

Postby AstroOafAdventurer [OP] » September 16th 2020, 5:08pm

Thanks to the trusty FSM, I looked up electrical diagnosing and found the low pressure switch.
Jumped, the compressor engaged so as suspected no AC due to no R134.
So what should I do, leak detect or dump some more refrigerant in?
As said above I put 2 12oz cans in, however I just checked and the 2nd can may be full.
If anyone could pipe up about common leaks or obvious things to check I'd greatly appreciate it. The extent of my AC work is adding refrigerant.
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Re: AC diagnosing help

Postby AstroOafAdventurer [OP] » September 16th 2020, 6:24pm

So I went out, fired it up and added the remainder of a can. It built pressure up to green and then started dropping back down. Compressor never engaged, I shorted the low pressure switch and tried again, and sprayed some soapy water around what I could see and nothing.
So I would assume I have a fairly large leak and not sure how to proceed as without the compressor running and pressure dropping so quick I don't know how to pressure test.
Can I leave the low pressure switch jumped to keep the compressor running?
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Re: AC diagnosing help

Postby N6KB » September 16th 2020, 6:40pm

If you have a gross leak adding more freon will result in having a mixture of freon, air, and water vapor in the system. Even if you fix the leak your system will be contaminated with air and water vapor unless you connect it to a vacuum pump to clean it out. One method I have found for finding a leak is to dribble alcohol on likely points of leakage while the vacuum pump is running. When the alcohol gets sucked into a leak the vacuum pump exit port will show vapor as the alcohol expands in the low pressure. When you do this you must work slow and be patient. It may take a half a minute for the vapor to show coming out of the vacuum pump after you get the alcohol on the leak. If you work too fast you will get confused about which place you put the alcohol is actually the leak. Once you get a response you may need to wait a few minutes for the vacuum pump to recover before you can try again or try another possible leak location.
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Re: AC diagnosing help

Postby AstroOafAdventurer [OP] » September 16th 2020, 7:21pm

Will one of these work?
https://www.harborfreight.com/air-vacuu ... 96677.html
I have a pancake compressor to use with it.
Thanks, I was really scratching my head wondering how to pressure test with no pressure lol
Edit: I was searching further on leak detecting and found a vid of a guy adding refrigerant with the engine off and heard the leak, then found it with UV dye.
I saw someone here on another topic say they filled their system up to a high psi and heard it as well.
Is it easy to connect an air compressor to pump it up for an auditory clue to the leaks location?
If I have to vacuum it out anyway, figure it might be worth trying
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Re: AC diagnosing help

Postby N6KB » September 17th 2020, 7:30am

Yeah that pump would probably do the job. My personal preference would be one with an electric motor. I have the $89 Pittsburgh (made in China) one on the same page. It's a cheesy little thing, but it works.
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Re: AC diagnosing help

Postby AstroOafAdventurer [OP] » September 17th 2020, 1:55pm

HF doesn't have gauges on their site anymore, got a cheapo set coming from Amazon.
I'm heading out to get the pump now.
Thanks for the help, while turning out more costly that was hoping, still cheaper that the shop. They told me ac diagnosis start at 200 an hour, plus parts, plus refrigerant.
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Re: AC diagnosing help

Postby AstroOafAdventurer [OP] » Today, 2:17am

Found it's leaking at the compressor, either the case or where the lines attach.
Either way I'll replace the compressor and drier.
Is there a brand I should look for?
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