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Old 06-12-2007, 09:09 PM
saumil saumil is offline
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Join Date: Aug 2001
Location: Houston, Texas
Posts: 393
Make sure there is no leak in the system before you take the compressor apart. Compressor could have failed because the oil may have leaked out over a period of time. If there is a leak, hopefully it is not behind the dashboard (I had it there and it took me months to finish the job).

I have changed from R12 to R134A on a 1987 260E a few years back. The steps are:
1. after removing the compressor and drier, flush the system a few times using compressed air and genuine flushing fluid, dont sweat to get all the oil out (thats what a mechanic at the dealer told me).
2. replace drier and compressor, make sure you use MB O-rings. MB O-rings are designed to withstand higher pressures of R134A. Use a rebuilt compressor, Hancock compressors are great. I have used them in two other cars (ML320 and Honda CRV). Use a MB drier.
3. use Ester oil in the compressor so that the remaining old oil will not cause a problem.
4. replace the schrader valves for low and high pressure sides, use MB valves
4. Vaccum and recharge with R134A
Caution: Do not use the gauges that you might have used for R12, use a new set of gauges. Also there is no need to change the valve adapters, leave them as the schrader valves.

R134A may take slightly longer to reach the cooler temperatures, but the convenience and cost of R134A far outweighs the benefits.

Good-luck
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Saumil S. Patel
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