1991 Suburban AC

[oldretiredafguy]

Getting the 1991 Suburban V-1500 put back together. We've already sourced new evaporators F&R, Dryer, Condenser, Orifice tube, Rear Expansion Valve, and all electrical switches/relays. Still has the original R-4 compressor installed. question is about the correct oil to use when going from R-12 to R-134A, and whether or not the compressor needs to be changed out.

As far as the correct oil to use, went down to the local parts store (OReilly's) ad asked the question, they said to use medium viscosity Ester Oil, and sold me this:

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As far as the compressor, I've read lots of threads on AC compressors, and found there are a thousand opinions and info. My body shop guy is doing all the mechanical work, and really doesn't like to get into changing lines, having new lines made etc, etc, etc. I have no idea if the old one is good or bad-can they be tested reliably?

 

[Midnightmoon]

I would have thought that PAG would be the proper oil for 134a. I reserve the right to be wrong however.

 

[oldretiredafguy]

I would have thought that PAG would be the proper oil for 134a. I reserve the right to be wrong however.

I thought the same thing. This came from the O'Reilly Tech Support folks, who supposedly hire only the best and brightest for these Tech Support jobs.

 

[AuroraGirl]

I thought the same thing. This came from the O'Reilly Tech Support folks, who supposedly hire only the best and brightest for these Tech Support jobs.

GM r134a uses pag oil. You are maybe safe if your system is perfectly clean and your o rings and compressor are compatible.
If you had any mineral oil or things not compatible with ester,
But it seems ester oil is the oil gm would use in a conversion scenario, so maybe thats the right thing. its synthetic and compatible with both r12 and r134a.

 

[bucket]

I always always always use PAG 150 oil with an R4 compressor on an r143a system.

 

[AuroraGirl]

I always always always use PAG 150 oil with an R4 compressor on an r143a system.

for the viscosity reasons?

 

[Snoots]

I always always always use PAG 150 oil with an R4 compressor on an r143a system.

Is that r143a the Pumpkin Spice variety?

 

[bucket]

for the viscosity reasons?

Yes. Every R4 on the planet seems to be made with very loose tolerances.

Is that r143a the Pumpkin Spice variety?

Only if purchased in the fall, lol.

 

[oldretiredafguy]

I always always always use PAG 150 oil with an R4 compressor on an r143a system.

Thanks-that's what I thought, until I found this paragraph on Advance Auto website for converting a R-12 system to R-134A, and I quote:

Add the proper Ester or PAG oil to the condenser, compressor and evaporator if necessary. Ester oil is often recommended for use with retrofit systems because it can mix with any remaining traces of mineral oil or R-12 and still lubricate the system properly.

 

[AuroraGirl]

GM r134a uses pag oil. You are maybe safe if your system is perfectly clean and your o rings and compressor are compatible.
If you had any mineral oil or things not compatible with ester,
But it seems ester oil is the oil gm would use in a conversion scenario, so maybe thats the right thing. its synthetic and compatible with both r12 and r134a.

Thanks-that's what I thought, until I found this paragraph on Advance Auto website for converting a R-12 system to R-134A, and I quote:

Add the proper Ester or PAG oil to the condenser, compressor and evaporator if necessary. Ester oil is often recommended for use with retrofit systems because it can mix with any remaining traces of mineral oil or R-12 and still lubricate the system properly.

we thought the same thing, go team lol. to be clear, your system had r12 and mineral oil in it before, yes? not 100% refreshed?