Hi all,
I would like to upgrade a clients 1974 SL450 A/C system. Are there any suggestions to improve the efficiency or replace components?

Thanks,
Dokta

UPGRADE? The only upgrade necessary would be if it has been changed to a refrigerant other than R12.

If it's still on R12 and not cooling well, check pressures and functionality. Post low and high side pressures, ambient temp at the time of their reading and vent temp. We can then go from there.

If this system was changed over to R-134 and the expansion valve was not changed that could be the problem.

But you have many test to run on this. It may just be a worn compressor.