Fan clutch not engaging, and no DTC or warnings

[Beast2B]

I got the chance to tow my new 5th wheel toyhauler this weekend at about 11k lbs. All was great until coming up the first medium sized hill. I was watching the trans temp on the cluster and noticed the coolant temp gauge climbing. Coolant got to 230 with no bells/buzzers/alarms/dings/DTCs, and no fan clutch engagement. I have heard the fan clutch before on my truck around 215-220, but I have not had the opportunity to tow heavy for a couple years (under 5k lbs lately). By the time I made it to my destination, I had gotten the truck to nearly 240 under my control (I backed out to drop it fairly quickly). never saw any indications, no codes set or in history and no lock up of the fan clutch. I am running EFI Live on the stock setting, but have gotten confirmation from the tuner that nothing to do with the fan clutch, or its control, are modified. I have a new fan clutch en route, but I'd love to troubleshoot it as much as possible before throwing expensive parts at it. I have access to a Snap-On MODIS that will show me fan speed and commanded fan clutch PWM%, but without the load I get zero PWM% (even with A/C on max). Fan speed increases as RPM increases, but I don't have a way to manually engage the clutch. Can a dealer do that? I will try removing the EFI Live and go to my back up Smarty to see if anything changes. Thoughts, ideas and experiences welcome!

 

[Bob4x4]

I have seen a fair amount of fan clutch failures in the 10-12 m years without codes some were very intermitant

 

[Beast2B]

Thanks. Sucks to throw parts at it, but I ain't skeered!