So today the 300D got up to the 120 degree C mark, very unusual. I found that the belt that goes around the water pump and the alt. was loose and replaced it, problem solved, now runs a about 80 degrees C(I added some Red Line Watter Wetter and it dropped the normal operating temp about 10 degrees).

My question is that when the engine was up near the 120 mark, the aux fan did not engage. It has worked in the past but this is the first time that the temp has really gotten over 100C and from my understanding the temp has to get to a certain degree to engage the fan. I know that there are some 'Ice Box' relays, on top of the drivers fender well, that may have some control on the fan, and have taken the relays and made sure they are getting power, which they are. I also check the aux fan connection under the front bumper and no power was getting there(with relays in of course).

From what I can determine the relay is the probable cause for the fan not working. I have also checked the fuse in the fuse box and it is ok, I replaced it just to make sure.

Am I missing something? Is there anything that I am missing that may cause the fan not to work?

__________________
1980 300D European
"The Red Fox"
200,000 miles

2003 Chevrolet Silverado

609 Certification