Recently the fan is fully engaged at start-up. This has not been the case with this truck until recently. This morning, the fan clutch did not disengage even while the truck was running at high idle while loading a Cat on the flatbed.

The clutch is not frozen. When the engine is shutdown, the fan can be rotated.

What could have caused this change? Bismic (I think) noted that the EGR system is involved with fan management. Could this be an early tell of EGR valve problems or is something else going on?

It is 40 degrees +/-.

Thanks in advance for your advice.

-Mike

 

Fan operation parameters are a semi-mystery but here's a bump for a tech. I don't think your problem is EGR related. Have you code scanned the truck?

 

On my 2007 with the plow prep package, my fan locks in using the SEIC wire to bump into high idle mode. I don't know why it's locking up at start, but it might be staying locked because of the idle circuit you're using. Mine doesn't lock if the truck kicks itself up.