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Replacing AC compressor, oil capacity?


Old 06-20-2014, 07:21 PM
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Replacing AC compressor, oil capacity?

Hey guys, I'm replacing the air conditioning compressor in my 91 bird. It's a remanufactured unit from Autozone, I know it's preoiled but I'm not sure how much more pag oil I should add to it.

Also, I read that the accumulator should be replaced every time the AC system is opened. Is that true?
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Old 06-21-2014, 07:22 AM
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Re: Replacing AC compressor, oil capacity?

I believe you add 2oz to the compressor and when you put it on the car and hook everything up but the belt, turn it 10 times. Yes you need to replace the dryer and orifice tube. You also need to pull a vacuum on the system prior to charging. I'm not an expert, just observed what the guy did that fixed mine.
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Old 06-21-2014, 07:52 AM
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Re: Replacing AC compressor, oil capacity?

what you should do is turn your compressor that you take off upside down and let the oil in the compressor drain into a measuring cup, then add that same amount of new oil to your new compressor, those new compressors come with some oil but not much, then add a hair more for safe measures, Yes orifice tube and dryer need replaced, also blow lines out if you find any metal in orifice tube. Then pull a vacuum on ac system for 20 min, then close gauge valves and see if it will hold vacuum for 10 min, needle should not move at all, it should hold 30 hg of vacuumn
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Old 06-21-2014, 08:18 AM
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Re: Replacing AC compressor, oil capacity?

Yes the accumulator should be replaced. The orifice tube as well.

If you're putting R-134A back in it, use the Frod red/orange one, not a GM one. Its orifice size is more appropriate to a GM R-12 system filled with R-134A, than a GM one.

Disassemble the system completely; every joint should come apart. Use 2 wrenches on every fitting to avoid damaging anything. If there is ANY evidence AT ALL of leakage (traces of oil) where a rubber hose meets a metal tube, REPLACE IT NOW; leaks NEVER heal themselves, and it makes no sense whatsoever to spend all this money and do all this work and leave something doomed to fail in it. Flush the lines and coils each individually with a NON-RESIDUE solvent such as lacquer thinner, MEK, or denatured alcohol; NOT brake cleaner, electric motor degreaser, or the like. Or even, (horrors! use the right thing) AC system flush.

The system as a whole should get about 5 oz of oil. Use the medium weight PAG oil; the 100 is about right. Not 75 or 150. Pour about half of it into the compressor suction port, and the other half into the accumulator.

Assemble the system with all new O-rings lubed with fresh PAG oil. Pull a vacuum on it; once it gets down to 29" or so of vacuum, keep the pump on it for another half-hour or so, then turn it off and make sure the vacuum holds at more than 28" for another half- hour. If it doesn't, it won't hold refrigerant either, so stop and find & fix the leaks.
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