Hey hey! I’m planning to bring my truck into the garage soon to hopefully quickly fix an issue that arose following replacement of a bad radiator fan bearing about a month ago at a shop down near Brownsville. The truck sounds great now, but immediately after the service the AC worked poorly while idling & the truck coolant reliably approaches overheating when not moving fast in 80+ degree weather. Overheating risk is mitigated by turning off AC & allowing the truck to idle faster by shifting to N while stopped. I was hope the techs only replaced the bad bearing. It seems they may have replaced the bearing + clutch + fan with a non-Mopar part. I don’t think the radiator fan clutch is working properly – or something related to it is failing to cause the clutch to work properly. I’ve checked for error codes with a simple BT CANBUS module & found no obvious error codes. There is a 400W DC-DC charger which charges the 800Ah LifePo4 battery bank in the camper top. I don’t think that additional alternator load is causing the overheating – but it might be. Voltages while idling stay pretty consistently near 14V.
If anyone wants to help me debug this issue this week, let me know! My schedule is pretty flexible. I’ve got a few good test recommendations which will likely help me identify the bad part of the system.
I’m new to the space & not sure when the typical garage slow times are. Suggestions about when to bring it in to avoid a car jam would be welcomed. Thanks!
-Daniel Love
Without knowing the year model, this kind of thing can vary greatly, but knee-jerk reaction to having skimmed your post, sounds like the electric override for the fan clutch isn’t working properly. Arguably, neither is the fan clutch itself, which should be plenty to kick the fan on before showing overheating on the gauge. That aside, here’s a pic from a fan clutch that 'zon claims will fit some models of RAM 3500 Cummins:
The electric connections are clearly visible on that shot, and making sure it’s plugged in would be my first stop, followed closely by making sure it works as-intended (power on A/C and this should complete the circuit, causing the fan to spin full-speed with engine idling regardless of coolant temp - but this should be testable KOEO, without the engine actually running, so more shop-friendly).
Hope it’s as easy as plugging it in! 
Before noonish on weekdays is usually slow.
You can check the cameras for confirmation.
https://dallasmakerspace.org/cam/
Scroll down to Automotive.
Fan spins freely while engine off, so clutch is probably not locked up. Serpentine belt seems to be routed properly. Connectors appear to be well-seated & wires in good condition. Wondering if there’s supposed to be a sensor where the suspicious zip tie is, in the pic. Researching now…
Looks like the clutch assembly is partly broken. Based on this product there is a piece of metal that extends from the engine block to the clutch assembly to help steady the assembly. Right now the assembly is only kept from spinning by the wires attached to it. Not sure if that would cause an issue. If there’s a sensor in the assembly it may not be able to get accurate readings.
Fabbed a temporary piece to take the strain off the cables & hopefully make the assembly more stable. There appears to be an optical encoder on the assembly & any sort of wobble might have negatively affected readings. Also sanded the connector contacts a little. So far so good. Not sure if the cooling issue is fixed, though. TBD.
In my tests, I’ve been unable to direct the clutch to provide maximum resistance. When I turn the engine on, the fan seems to rotate at the same speed as the serpentine belt. Is it common for there to be hidden gearing that allows the radiator fan to spin faster than the serpentine belt? Turning on the AC to full obviously adds a little load to the engine, but no observable change to belt or fan speed.
The overheating issue seems to persist. There seems to be a moderate improvement in how frequently the radiator fan clutch engages. I think I’ll probably need to take it to a regular auto shop soon. It needs fuel filters changed as well. The overheating issue could be a water pump issue, air in the coolant system, possible blocked radiator or possible fan comms issue. The overheating issue became evident immediately after the radiator fan bearing was replaced at an auto shop in south TX, leading me to conclude it is probably something related to the fan or improper routing of the serpentine belt. Local shop recommendations would be appreciated. Thanks!