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a/c what oil for 134 conversion

91eb4x

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san diego, ca
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91 eddie
I have a 91 explorer factory a/c thats been converted to 134 from previous owner..... I did a motor swap the lines where leaky so I got new replacements 94 style, and a new accumulator/drier for a 94(134) what type of oil do I use? pretty sure its pag but what weight? whats is the quanity for a 94 system? also should I change the switch not sure if its 134 style. previous owner said a/c worked good but lost charge.... thanks for your help in advance
 



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The main A/C line is different on a 94, with an electronic connector. It's usually way more expensive than the 91-93 R134a conversion line, too.

Most Ford systems used PAG 46 oil, though some R12 to R134a conversions use Ester instead of PAG oil. You can probably use PAG if you flush the evaporator, condenser, and have a new compressor, lines, and receiver/drier. Amount depends on the system, usually it's something like 8oz in the compressor (but be careful, some new ones already have oil in them), 5 oz in the receiver/drier (again, some already have it), or some amount in the system as a whole that you just split between them.

You should get a R134a switch. Factory air/four seasons makes one just for the 91-93 conversion, with an R12 connector so it works with the aftermarket replacement R12/R134a receiver/drier.

The original systems almost always lose their charge due to the O-ring seals leaking. You may want to use some Nylog O-ring lube on your new system to prevent this (and be sure to ONLY use the green o-rings too, not black rubber ones), or at least lube them with whatever oil you wind up using.

You also may want to get a new compressor, or a rebuilt from a 94. There are some reports that the stock compressor on the 91-93's aren't strong enough to deal with the pressures of R134a. They are ~$200 new, but it's cheaper than replacing the entire system and redoing everything due to a blown compressor.
 






the line I have goes in front of the compressor now that you say that I think for 92 and newer. im not partial to pag I just thought thats what would have been in there I'd like to put what ever they put in when they converted it. but I have no idea I can't read anything on the conversion label. the acc/drier I got is from a 94. I got the liquid line as well and a new motorcraft orifice tube. I remeber I used to put 2 ounces in the line and some in this and some in that like you said . I know its best to measure what came out , but I got the exploder in pieces so I couldn't.
 






so will ester oil work better? when doing a conversion??
 






Ester oil works "better" doing a conversion from R12 to R134a since it absorbs less moisture than PAG, and won't interact much with any left over mineral oil from the previous R12.

If you're dealing with an already-converted system that had R134a in it, and you're just replacing the hoses and everything, you're stuck trying to figure out what was used, hence why it's a heck of a lot easier flushing the evaporator/condenser and then with a new compressor and all new lines and a receiver/drier, you can use your choice.

Maybe you can drain some fluid out of the old receiver/drier or the compressor and try to determine what it used.

You'll probably be ok either way using PAG46 or Ester as long as you flush the evaporator/condenser anyway to clean them, drain the compressor fully and rinse-drain-rinse-drain it a few times with whatever you decide to use, and of course use a new receiver/drier. Then just be sure to use the correct amount of oil for the system and add it to the compressor, (letting it sit on the pulley end for a good while so the oil gets to the bearings and such parts) and receiver/drier.


There is only so much you can do other than removing parts to flush and clean, or just replace everything. Generally if you take the time to do a thorough job, it should be fine, and work about as good as it's going to for a converted system.
 






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