When my truck was newer the fan clutch sound like a jet when it kicked in. A few years ago I had a problem heating while towing a steep grade at a low speed. I replaced the fan clutch with a after market (Hayden) and I have never heard it kick in. My temp on a slow steep grade runs high and never hear the fan clutch kick in. Is it bad? Is there a way to test it?

 

Lenn, I had the same experience last year. I initially replaced t-stat with a NAPA, really got hot then. Went to Cummins and temps came down somewhat but then I noticed that the fan wasn'r roaring like usual, again, replaced with NAPA. Leaving next week for a trip to Texas, if it gets hot guess I'll stop in at Cummins and quit buying aftermarket parts for a Cummins.