Automotive Air Conditioning Information Forum

So I very successfully converted my 1991 Mustang GT's ac system to R134a back in 2008. I kept the OEM condenser and compressor. The accumulator, evaporator and all hoses were replaced with new. I flushed all of the OEM components, put in ester oil and after the conversion (and installation of an OEM Lincoln MK VIII electric radiator fan) I saw 40F vent temps in Florida summers.

Fast forward to today and I'm now working on my LS3 swapped '91 Foxbody coupe. The GT is gone but I kept the entire ac system. The compressor, evaporator and condenser are already installed in the coupe. I'm planning to make my own ac hoses since the compressor is in a different position on the LS3 engine and I'm going to buy a new accumulator.

I'd like to run PAG oil since I've already got about 5 bottles of it sitting on my garage shelf. I know that ester oil is compatible with PAG and mineral oil so I'm assuming that I shouldn't have any problems with it in this system. With everything apart,if needed, I shouldn't have any trouble flushing the evaporator and condenser. I can also "flush" some PAG oil through the compressor.

Please let me know if you think that this will work.

BTW, 13 months ago, I completely rebuilt the ac system in my 2002 Pontiac Trans Am so I have recent auto ac work experience.

Definitely flush the old oil out of the compressor with some fresh PAG if it has been sitting.

https://www.autoacforum.com/messageview ... adid=12050

As for the system, do what you did before. Use the right quantity of oil, charge it the same way you did before.

Sounds like a fun car

bohica, I know you responded to my question just over a year ago but I just saw your post. Hopefully I'm going to be doing the ac work on this car later in the spring after I get the car on the road. I will definitely flush the oil out of the compressor. Since I'm reusing the evaporator, I'll flush it with solvent and let it dry.

I have another thread on this forum where I asked about a parallel flow condenser vs using my original, R12, OEM Ford condenser. I'm leaning toward the extra efficiency of the parallel flow condenser. That OEM condenser will be another item that I won't have to solvent flush.

dannyual320 wrote: ↑Sat Feb 11, 2023 6:08 am ... Hopefully I'm going to be doing the ac work on this car later in the spring after I get the car on the road. I will definitely flush the oil out of the compressor. Since I'm reusing the evaporator, I'll flush it with solvent and let it dry.

Sounds good. Then go ahead and add PAG oil in the appropriate amount and viscosity.

dannyual320 wrote: ↑Sat Feb 11, 2023 6:08 am I have another thread on this forum where I asked about a parallel flow condenser vs using my original, R12, OEM Ford condenser. I'm leaning toward the extra efficiency of the parallel flow condenser. That OEM condenser will be another item that I won't have to solvent flush.

I usually hold onto my own OEM components, provided that they were working well previously and are in good condition. Nothing wrong with installing a new parallel-flow condenser, but you might consider keeping the OEM condenser as well. If you decide to keep it, do this when you have time: Flush it well with solvent, blow it out, let it dry in the sun for a few days, give it a final blow-out with nitrogen (if you have it), securely cap the tubes, then put it away in the box the PF condenser came in.

I've been thinking about the new, parallel flow condenser vs using my good, OEM quality R12 condenser. I like the idea of the parallel flow but chinese made stuff really doesn't give me confidence.

At the moment, I'm leaning toward just flushing my OEM condenser and using it.

dannyual320 wrote: ↑Mon Feb 20, 2023 7:14 pm I've been thinking about the new, parallel flow condenser vs using my good, OEM quality R12 condenser. I like the idea of the parallel flow but chinese made stuff really doesn't give me confidence. At the moment, I'm leaning toward just flushing my OEM condenser and using it.

What you could do is purchase the imported, relatively inexpensive PF condenser, install it, and see how it runs. If it proves to be problematical for whatever reason, at least you will have kept your original OEM condenser, which you could then re-install—as long as you don't mind having to recover, evacuate, and recharge the system again. I seem to recall from your other thread that the OEM unit performed very well with R-134a.