AC Electrical Problem
 

My AC won't work because the compressor won't come on because, apparently, my compressor relay is not getting a TD (rpm) signal. I'm told this is sort of a safetly feature - the compressor relay compares the engine rpm to the compressor rpm and unless they are the same the compressor won't come on. So my compressor won't come on because it's not getting the engine rpm signal. I realize this is an obscure question but does anyone know where that engine rpm signal comes from, and what might be causing the failure. The wiring harness was recently replaced but I know the AC worked for a while after that.

Year and model please...:confused:...and engine if known...

Yes, we find such information to be quite helpful.

Have a great day,

Boy you guys are fast - I had already realized I forgot the model info, logged back on to edit it and found two posts already. The car is a 1994 E320 coupe, 104 motor, the tach is working fine. Thanks.

I hope you get it fixed soon, Phoenix is about to become an oven. The car is white, isn't it?

No, no - the car is black. But when Phoenix turns to an oven, which is a little more than half the year - I leave. But I thought I had it sold to a year-round resident - but the deal fell through - so it's become a low priority project.