1 more a/c q?
Thread Starter
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Fleet Mechanic
Joined: Dec 2006
Posts: 1,338
Likes: 6
From: UPSTATE NY
1 more a/c q?
what should the pressure readings be on both low and high gauges for optimal r134a charge? i went through all retrofit procedures, fixed leaks, and pulled a vacuum. it has like 2 cans in it right now and i need to figure out how much more to put. my low fitting readings are below zero and my high fitting readings are at 130. i cant find the specs for this system or vehicle and my chilton has nothing a/c in it. the tag on the compressor says 2lbs of r12. this compressor is brand new and i put proper oil in it too. its the same exact remanufactured replacement for what i had.
Elder User
Joined: Jan 2008
Posts: 658
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From: N.W. Mo.
You should need about 80% as much R-134 as it used with R-12.
If you have 2 cans in it that would be 24 oz. That should be real close. If you are pulling the low side into a vac with it running there must be a problem somewhere. Was it working ok before you switced it over?
If you have 2 cans in it that would be 24 oz. That should be real close. If you are pulling the low side into a vac with it running there must be a problem somewhere. Was it working ok before you switced it over?
Thread Starter
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Fleet Mechanic
Joined: Dec 2006
Posts: 1,338
Likes: 6
From: UPSTATE NY
yes with my old compressor we got it pretty cold with 2 cans. then the compressor blew. we were able to vacuum it down a little better this time now that i fixed the leaks. but that wont cause it to consume more freon during an initial charge would it?
Elder User
Joined: Jan 2008
Posts: 658
Likes: 0
From: N.W. Mo.
Properly evacuated the system should take only the required amount of freon.
What vehicle are you working on?
I would think that you may have a plugged exp. valve or orfice tube depernding on which type system you have. Possibly from debris from the old compressor. Did you flush the system?
What vehicle are you working on?
I would think that you may have a plugged exp. valve or orfice tube depernding on which type system you have. Possibly from debris from the old compressor. Did you flush the system?
Fleet Mechanic
Joined: Aug 2007
Posts: 1,842
Likes: 264
From: Piney Woods of East Texas
All readings must be with the fan on HIGH Speed, and I prefer around 1200-1500 rpm if you have good cooling fans.
I always charge by vapor temp on fixed orfice systems, which puts you in the 28-30psi range for 32F. This keeps the water from freezing on the coil. On expansion valve system they control by suction line temp which prevents freeze ups so they are more forgiving. On retrofit system I would charge by weight, 60-80% of R12 requirements if only the refergerant was replaced.
With your numbers it appears to be under charged. If the fan was not on High it will give you lower numbers on the low (suction) side. Put a thermometer in the registers and check for temp. The R12 was capable of 35F is every thing was right.
I always charge by vapor temp on fixed orfice systems, which puts you in the 28-30psi range for 32F. This keeps the water from freezing on the coil. On expansion valve system they control by suction line temp which prevents freeze ups so they are more forgiving. On retrofit system I would charge by weight, 60-80% of R12 requirements if only the refergerant was replaced.
With your numbers it appears to be under charged. If the fan was not on High it will give you lower numbers on the low (suction) side. Put a thermometer in the registers and check for temp. The R12 was capable of 35F is every thing was right.
