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How much oil does a new A/C system take?

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Old 05-13-2006, 06:19 PM   #1  
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How much oil does a new A/C system take?

I searched for this ? but didn't have any luck, I'm getting ready to bolt on a new compressor, accumulator and convert over to 134A and I bought 2- 2 oz. cans of Ester oil, is that too much, not enough? And how many cans of 134A does it take? I have 3, and is it 100% necessary to pull a vaccume on a system? I have heard of doing it without, but I'll go borrow a vaccume pump somewhere if it's 100% needed.
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Old 05-13-2006, 08:31 PM   #2  
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You'll want to pull at least 10" Hg on the system for 20 minutes at room temperature just to make sure it's dry (no moisture).

What compressor? Is it precharged with oil? An R-4 compressor bone dry in a typical Frigidaire auto system used to take 6 ounces of oil. Older systems with driers on the high side used to take a bit more.

Make sure the system is cleaned out of the old (mineral) oil. Add two ounces of ester liquid to the low side fitting at the compressor, rotating the compressor if necessary to add the oil. Attach the hose manifold with it's 'O' rings to the back of the compressor, then rotate the compressor at least ten turns to distribute the oil. Connect the vacuum pump and evacuate the system to 10". The oil will remain, but any water should boil off.

With the system sealed and evacuated, add at least one can of the oil to the high side (at the compressor if possible) if you can, and one can of oil to the accumulator/low side fitting. Add about a pound of refrigerant, then try to cycle the compressor. Fill to required pressures with more refrigerant. Done.
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Old 05-13-2006, 09:00 PM   #3  
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It's a rebuilt Murray compressor, says it's been 100% pre-tested so I assume it already has some oil in it, the instructions say to add the correct amount but does not give details, so I guess I need to go scrounge up a vaccum pump somewhere and get 4 more oz. of oil to have enough in it, thanks
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Old 05-14-2006, 10:03 AM   #4  
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That would be 2 more ounces of oil. Make sure the oil left in the compessor is not mineral oil. If it was rebuilt, and intended for an R-12 system, that might be what was used to test it. If so, you'll need to clean it out or risk wax precipitation when you mix it with ester.

Your other option is to forgo the 134A conversion and use R414-B.
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Old 05-14-2006, 12:00 PM   #5  
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Well the instructions were crappy, but it did say to use either R12 or 134a so I guess whatever oil was in it is compatable, anyway it's all installed now, I borrrowed a vacuum pump and pulled the system down, I've put 6 oz. of ester oil in it, I hope that's enough, it's all working now, seems to cool pretty good, the compressor is getting pretty warm, but not so hot you can't touch it for a few sec. is that normal for a new tight compressor? I don't remember the old one getting very hot. It has a 1 year warranty so if it does crap out I can get a replacement, and I didn't return the old original compressor, as it was still in pretty good shape but the clutch was toasted and it leaked a little oil, is it possible to rebuild them at home? That would be a neat project to do someday, I've kept all the rebuildable parts that came on the car new, planning on rebuilding them all one day.
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Old 05-14-2006, 01:08 PM   #6  
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6 ounces of oil should be adequate, AFAIK. If the compressor was rated for either refrigerant, that would IMPLY that the oils were compatible. If they used a different synthetic, it might work for either. You'll find out in a year or so. If the expansion control doesn't get clogged, it's probably O.K.

Given the operating pressures of R134A, it should get fairly hot. Without knowing the actual temperature, that's probably normal.

You can repair compressors. If it was leaking oil, it was probably leaking refrigerant as well. The valves are simple. If the pistons are servicable, you can install new seals and a clutch and probably have a good spare. If there is piston clearance beyond a couple thousandths, it's probably junk. Disassembly could be a little tricky, however.
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Old 08-09-2017, 11:35 AM   #7  
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Re: How much oil does a new A/C system take?

Hi all
Read various threads but still very confused. Also reading my 85 camaro shop manual (also confusing)
Have assume original Harrison compressor model # 1131529 which says refrigerant oil 6 oz.
System was converted to 134a by expert shop approx 15 yrs ago, 6 years ago started restoring engine compartment incl remove emissions.
Removed A/C stuff for cleaning and paint back then, when I took apart for cleaning, 134a was released into ozone layer (not good), compressor has been drained by setting upside down during painting and also prior to reinstall. Just bought a new accumulator, oring kit and valve/cap kit.

manual shows r-12 info on oil for each component, if you add these up it comes to 7 or 8 oz, not 6 oz which I assume is for the entire system, as it says that not much oil is retained in compressor, THUS

Given my original compressor, new accumulator, evaporator left in place, and condenser was removed, cleaned and painted:
1. how much oil would you add to each component and where?
2. what viscosity? (r-12 oil said 525 viscosity), whereas Pag oil options are 50, 100, 150 i think
3. Should I get pag oil with dye or buy separate, or ester oil and is this different then Pag?
Note: retrofit sticker only says "performed to SAE J1661" nothing else was filled out by shop back then
thank you for your help
tom

Last edited by tom1985; 08-09-2017 at 11:40 AM.
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