I have been trying to figure out why my benz is overheating when climbing up hills or going fast. I think it may be fan related.

A few questions....

1. When does the aux fan engage (besides when AC is on)? At +100C?

2. When does the engine fan clutch engage? Does it run all the time? At cold start up, my fan is spinning and I cant stop it with a towel. Ive heard that it should be free-spinning.

3. Do the fan and aux fan share a control switch? Where is this located?

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'87 300TDT 150k