Aux fan turns on at normal operating temp.
 

Noticed that the aux fans of my 1990 300SE turn on when the engine is at normal operating temperature of 80*C with no AC. This happened in the last three days, any suggestions of what could cause this? Now that I think of it, it started doing this after I ran the AC for the first time since the summer.

Dirty and/or loose connection at the temp sensor or a bad sensor. As resistance goes up the fan comes on at a lower temps.

Good luck!!!

Thanks, will check!

Do they come on at high fan speed or low fan speed?


if at low speed then check the switch on the a/c receiver drier (when it's closed the fans run, there are 2 sensors only one does fans)


if at high speed then check the sensor on the cylinder head

Looks like it was the switch on the block for the high fan speed. I think it must have come loose, wiggled it last night and the fan didn't come on this morning after an hour of city driving.

What color is your 300SE?

441 Desert Taupe


I really liked the black on black combo I found but it had 250k and needed a tranny. But the interior was like new

That's a nice color. Wanted a black on black W126 as well, just like my old 300CD. But I'm very happy with my grey interior, it's a little dull but makes the interior more spacious feeling and cleaner.