My shop has done near a thousand R12 to R134 conversions. I personally hate them and keep my best customers from making that decision.
We have been doing this for ten years and have changed many of our practices. The most significant is to change from ester to PAG 46 for Nippondenso compressors. We didi this at first to stay with MBs warrantee requirements. Later after much discussion and research we decided that the viscosity of the ester oil was wrong for those compressors (Its all right for the GM R4 and A6 compressors and we still use it there). Our retrofits are much more successful now that we have changed. I say that after almost two years and two summers worth of experience with the new procedure.
I smile as I read of individual success stories. After about the first 700 retrofits, I finally had enough feedback info to draw a number of conclusions:
1) They absolutely DON'T cool as well. Maybe close in 75% of cases.
2) They will take out at least the compressor seals within two years (If a new compressor is not installed at the same time).
3) They get worse over time and can not be repaired without wholesale replacement once they get to the real poor condition. I have presumed many of these problems are due to chemical insulative properties aquired through oil/flush, oil/oil, oil/refrig, refrig/refrig instability. I got a call the other day from a top BMW tech in Pittsburgh. He wanted my Southern experience on retrofitting as BMW says not to do it on certain aluminum evaporators because of a corrosion problem. I told him not to worry and then started to worry myself. I have vast experience and it is insignificant in so many ways when it comes to long term evaluation of re-engineering a system.
BTW, our shop 280TE which was our guinea pig, still works marginally on the new compressor and retrofit we put on it in 1991 (the York was replaced with a Sanden), with no additional work. We retired the car two years ago and one of our techs still drives it.
Bosch Master, ASE Master, L1
33 years MB technician
Last edited by stevebfl; 09-01-2001 at 09:47 AM.