97 Suburban 6.5td. No aux fan, big honking clutch fan. Maybe the clutch fan should engage sooner but engine temps are in check per the gauge so I'd rather not mess with it.

I'll put a test light on the MB to see if the aux fan comes on when the car is moving. I doubt it since the aux fan doesn't blow all the time the compressor's engaged with the car idling. I expect air flow through the condenser at speeds above creeping in traffic keeps the high temp switch quiet.

I'm glad to catch LMG's attention How do I trigger the fan more selectively than when the compressor's engaged?

Sixto
87 300D