how much refrigerant and lubricant goes in after a 3800 swap?

same as a 4 cyl or a 2.8. Vacuum the system for about 20 minutes, (after you have Ester Oil in it) then install 2 12 oz cans of 134. you're done.

quote Originally posted by Lou6t4gto: same as a 4 cyl or a 2.8. Vacuum the system for about 20 minutes, (after you have Ester Oil in it) then install 2 12 oz cans of 134. you're done.

2.5 lbs (Original Fiero R-12 capacity) X 90% = 2.25lbs refrigerant (~3 12oz cans)

8 oz oil. Type depends on the compressor, can be PAG46 or PAG150. Using the Fiero compressor or the 3800 compressor?

-Reuse known working compressor, or buy new. Reman's are usually rebuilt in China by 8 year olds who don't know WTF they're doing.

-Replace accumulator

-Replace orifice tube

-Replace o-rings, lube with 525 viscosity mineral oil, even if converting to R-134A (PAG oil is corrosive).

-Vacuum down system for 30 minutes MINIMUM. Close manifold valves and check for pressure drop.

-If good, start adding refrigerant BY WEIGHT!!! System should start cycling into the second can. Best to get the system recharged by a professional with professional equipment if you can find a guy who will touch a Fiero or a retrofit.

-Reusing the Fiero compressor? Adjust the cycling switch of the accumulator so it kicks on at 21psi instead of 25. Using the 3800 3-pin switch? ECM should be controlling the system.

quote Originally posted by RWDPLZ: 2.5 lbs (Original Fiero R-12 capacity) X 90% = 2.25lbs refrigerant (~3 12oz cans) 8 oz oil. Type depends on the compressor, can be PAG46 or PAG150. Using the Fiero compressor or the 3800 compressor? -Reuse known working compressor, or buy new. Reman's are usually rebuilt in China by 8 year olds who don't know WTF they're doing. -Replace accumulator -Replace orifice tube -Replace o-rings, lube with 525 viscosity mineral oil, even if converting to R-134A (PAG oil is corrosive). -Vacuum down system for 30 minutes MINIMUM. Close manifold valves and check for pressure drop. -If good, start adding refrigerant BY WEIGHT!!! System should start cycling into the second can. Best to get the system recharged by a professional with professional equipment if you can find a guy who will touch a Fiero or a retrofit. -Reusing the Fiero compressor? Adjust the cycling switch of the accumulator so it kicks on at 21psi instead of 25. Using the 3800 3-pin switch? ECM should be controlling the system.

Agree with most of what you have said but on R-134a conversions I prefer to use Ester oil. PAG oil may be better but it MUST be used in a completely clean system. The slightest trace of 525 oil will result in contamination and possible failure. Ester oil can tolerate and survive in an old system better, that contains traces of the old mineral oil. My 3800SC swap uses the GTP variable displacement compressor (model V7 I believe) which in theory was designed for use with PAG oil. Its been running perfectly for 6 years with R-134a and Ester oil . It runs quiet and it blows very cold on even 90* days.

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I agree with RWDPLZ. I installed PAG150 after flushing all lines (including the muffler line!) and they cool at 35-40 degrees all day long. One car I replaced condenser and the other I didnt but did flush it in the car.
There was a thread that GM recommends PAG150 for retrofits and that's what I went with. However, you lubricate the o-rings only with mineral oil. Did that too.