My '89 190E 2.6L has a weird pattern of aux fans behavior.

1. They come on within 10 seconds of a cold start, sometimes immediately.

2. They do turn off after a good amount of driving.

3. They seem to be on when the a/c is on.

The a/c drier switch is not connected to anything. P.O. must have disabled it. I think the only switch left to check is the 100C switch. Am I correct?

The fuse looks okay...the hi-speed relay was replaced 3 months ago.

Please advise if I can check anything else.

Thanks,
Michael

There is a blue 2-pole temp switch on left side of cylinder head that can cause fans to run. It sends temp readings to a/c pushbutton & it turns aux fan(s) on & can cut A/C compressor off.