After installing a new servo amplifier the A/C is working much better. In addition to no longer having heat coming from the side vents and floor vents the center vents are now working. It is actually putting out cool air instead of heat.

I went ahead and took a chance on the salvage yard servo being ok and installed the new amplifier. The store were I bought it said that if the servo ended up frying the amplifier they would warranty it. So there was no way I could lose.

What a relief. This is my first Mercedes and I know very little about these cars. I was starting to think about taking the car to a mechanic. That would have cost even more money.

I was wondering about the amount of oil to put in the compressor. Normally you put 8 ounces of oil in the system when install a new compressor (GM compressor). But a well estblished AC repair shop in the Dallas area, tells me that because of the design of the 300SD it is a good idea to use 10 ounces. Is this true given the design of the compressor being along the bottom area of the engine?

Thank you for all the replies. You have been a big help and I appreciate it.

Tony