I have a 1998 Mercedes E300 TD with 245,000 miles. The a/c unit puts out really cold air for awhile and then blows warm air. This does happen more when the temp outside reaches 80 degrees and up. It also seems to happen more when I am in stop and go traffic.

When it blows hot, I can turn the engine off for a couple of minutes and when turned back on the a/c is really cold again.

I have read the evaporator temperature sensor can fail, causing the AC compressor not to cycle. If the AC compressor does not cycle on, the AC system will not blow cold air. If the AC compressor is stuck on, the air will be very cold at first, before warming up.

Can I change the evaporator temperature sensor myself and where is it located?

Thanks for any help.

 

First I would make sure the compressor is actually disengaging when you get warm air out the vents.