Did a 3.8 swap and now I am doing the air conditioning. GM says to only use PAG oil in the compressor but others say to use only esther oil on a conversion . I am getting many conflicting ideas. What have people who have done this swap done and any problems or success that they have had?

Thanks much, car54

The 134 conversion uses PAG oil. Which one depends on your compressor. Best results if you pull lines apart and flush the system. Add correct oil to compressor and new dryer and inject the balance before the Freon. Be sure and use new green O rings.

Have used Ester oil in several R-12 to R-134a conversions and all were successful. You need to open lines blow them out , replace accumulator, orifice tube and use green O rings on any lines that have been opened. On lines left alone and not opened, you can leave the black O rings in place and they will hold. I also believe that with an R-134a conversion, that its a good idea to replace that 28-33 year old compressor with a new one. IMO, you are on borrowed time with a compressor that old.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 07-15-2016).]

I probably was not clear enough. I have a 2006 GM compressor that GM says to use PAG oil but I have read many things stating that you should use ester oil with a R12 to a R134 conversion. Will the ester oil cause problems with the GM compressor?

Thanks car54

PAG oil and Mineral Oil ( R12 oil) will not mix, and can cause issues. That is why a complete flush is important. However, it's nearly impossible to get all the old mineral oil out of a system, especially the evaporator and condenser. That is where Ester Oil comes in. It will mix with Mineral Oil, and is compatible with R134a. If I was not sure I could get 97%+ of all the mineral oil out of the system, then I would use Ester. That being said, I've always flushed mine to the point that I could use PAG oil. I think either solution will work fine. Well documented on the net.

Whichever one you use, get the one with the Dye. Makes tracing a leak so much easier. Put a few ounces (3) in the compressor, and 3 OZ in the accumulator. Once it is installed and the hoses attached, turn the compressor by hand a few revolutions to distribute the liquid oil out into the line, so you don't hydro-lock the compressor. With the extra long lines in the Fiero, an OZ or 2 more in the condenser is not a bad idea either.

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'87 GT in Swap process: '00 3800 Series II SC, 4t65e.

As I posted in my swap I installed a new GP 3800 compressor and basically converted my Fiero A/C to a 1999 GP A/C. Flushed the system and used the proper PAG 150 oil for that system. If you convert a Fiero A/C and don't flush that is different. But the original oil will not circulate in a 134 system. My new compressor came with 7oz in it.

On Fiero R0134a conversions it is likely that you will have small amounts of 525 mineral oil, and PAG oil left over. (if you use the GTP compressor). Still the R-134a conversions that I have all done with Ester oil have all worked out well . I have no idea why some people must have an R-134a conversion using PAG when a system oil charge with Ester oil works well and will last . It like GM recommends 5w 30 oil in a 3800SC but I use Mobil One 15W-50 oil for greater engine protection.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

PAG is ONLY for 134a from the factory, or EVERYTHING new. PAG and mineral will mix and turn to varnish, you want ester for any kind of conversion.
BTW you can't flush an evaporator, it has parallel tubes and a Reservoir in the bottom that can/will hold old oil and flush, not good.

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"DRIVE IT LIKE A FIERO"
'84 Fiero, engine to be determined '87 Duke (Sold)
'87 Quad 4 H.O.
'87Blue GT 3.4L Swap Completed!!!!!!!! Boosted!!!!!!!
^^^^ Now in the Construction Zone^^^^
Las Vegas Fiero Club Parts/Sales/Service/Club
Fiero Road Club Of Northern Nevada
Now on my 11th Fiero

Obviously if you are not confident in your flush or don't flush you should use esther oil.