Upgrading AC to 134a Questions

i have a series 2 v12 and im planning on upgrading the system to 134a as the title suggests. Right now Im in the planning stages. Ive been watching some youtube and had some concerns. my original plan was to save the evaporator and condenser cores and replace everything else. Now im thinking it might be necessary to replace both cores. according to a video i watched PAG oil for 134a is not compatible with mineral oil in r12 systems. there is bound to be traces of mineral oil in the cores no matter how well i flush them. Are trace amounts going to cause problems with the new compressor?

Jaguar recommended ESTER based oil as compatible with 134a in the R12 retrofit system.

82-39am R-134a Retrofits Kits.pdf (25.9 KB)

You might consider going to R152: @abercanadian has done it, with great success.

On charge day I was planning to use the r134a machine my employer is kind enough to let me use. unfortunately that thing is already loaded with PAG. i could drain the oil out of the machine and replace with ester but then theyll be traces of PAG.

unfortunately the OEM system is junk. the car sat in a barn for many years. the compressor is leaking and all the lines are dry rotted. was using this as an opportunity to upgrade to 134a since it all needs replaced anyway. Also thinking of moving the compressor out of the vee to where the smog pump used to sit. if i can find one that fits.

I did this on my XJ6s3. I replaced compressor with a Sanden, filter, TXV, and hoses, but kept the condenser and evaporator. If you disassemble everything and flush the components well using a flush bottle, you should be fine. After flushing, I blew the components out slowly with dry nitrogen. After reassembly, I pulled a very deep vacuum to boil off any residual flushing fluid and oil. Having a micro-gauge is very worthwhile. I just use PAG. After 8 years, no problems.



Replacing the evaporator is a sort of major operation, Alan - the rest is just a matter of money…

xj6 85 Sov Europe (UK/NZ)

A sanden 508 is high on my list of compressors to use for the job. I can get one thats a near perfect match for the vee in my v12. would just need to fabricate a mount. also considering other types that i might be able to squeeze into the space on the right side of the engine. its good to know that i can re use the evaporator and condenser like i had planned. this will save time and money. i tested both by pulling a vaccum on them and they seemed solid.

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I have found that Ron’s assessment to be true. Try to flush out best you can.
Yes, you will always have a small amount of the older oil in the system but it won’t matter as much as you think. I have done many conversions to 134a from R-12.
Most of the oil is in the compressor and a smaller amount are in the lines, use pressurized nitrogen or worse case just compressed air pushing through the larger suction hose and releasing pressure through the smaller hose (discharge line), but then definitely use nitrogen.
I would leave the nitrogen in the system for a day then flush out right before you get vacuum pump going.