Been trying not to post this issue in efforts not to duplicate, but have been looking for more than a week and not have seen anything similar.

1989 300E aux fan runs automatically in warmer temps. Cooler temps, I can start the car with aux fan off. By lunch time, start car and aux fan comes on with start.

This is new symptom, prior, worked the way it was supposed to.

Recent History (3 Week Span):

Replaced Fuel Pump Relay (car was stalling every few miles... thanks to forum for diagnosis and fix - first noticed aux fan running)

Driven car and noticed a smell of what I thought was anti-freeze. Pulled car over, checked for any leaks and was none. Got car home did thorough check and noticed the 25A fuse in the "D" slot had completely melted into its slot.

Removed and cleaned out all the melted plastic from the fuse slot and made sure a new fuse will have a good connection. Did not fix problem.

Replaced Blower Motor Fuse (interior fan did not blow in cabin after new FPR installed)

Ambient Temp Sensor Wire Reconnected (Severed wire pulling too close to curb)

Replaced Coolant Temp Sensor. Still did not fix aux fan issue.

I am now at a loss as to what is causing this aux fan to constantly run, especially in warmer temps. Thanking everyone in advance for any and all feedback and advice.

I believe the problem has been solved, thanks a million to a MB Tech here on the forum. I will know for sure tomorrow or Monday after I have an opportunity to drive it a while.

With the items listed above, the A/C temp sensor connector wires ended up being the culprit. The connection to the sensor was horrendous. Cleaned the connectors and the posts they attached to and soldered the wire onto the connector.

Will verify the fix shortly.