So if it is not the RPM sensor...
where do I look next. I have a '88 300E that is acting up.
In warm weather the A/C seems fine, and the car can get quite cold. However, when it gets into the high 90's and higher, the vents will blow cold air for about the first 10 minutes and then hot-humid air for 2 minutes then back to cool air. It seems like the compressor is turning it's self on and off. The hotter it is out side, the shorter the time it blows cold. It may cycle back and forth or just give up and blow hot air. This may have nothing to do with it, but sometimes the air bag light comes on and then goes out.
newbie- Mark Potter