fan will always turn, but it shouldnt be spinning flat out all the time. the viscous clutch is supposed to allow the fan to 'slip' (basically just rotate slowly). sometimes, over time they tend to tighten up a bit and can cause poor heat. with the engine off, juve the fan a spin and see how far it freewheels, if it stops almost instantly you have an issue
Mine wouldn't even get to the 140 mark. I got a new thermostat and seals from Cummins for about 40 bucks. Now everything is good. My fan is kind of stiff. I give it a push, It stops moving when I take off my hand.
98 Dodge 2500, 12 valve, bought it new. Now has 80,000 miles. Club cab, loaded, stock. A/C works fine. Cannot get adequate heat in cab in winter, you must have heavy winter clothes on to keep warm. It has had this problem since the vehicle was new. Dealer replaced thermostat and radiator cap, no change.Temp gage comes up barely into normal arc after 30 minutes, but still only cool to lukewarm air out of heater, and no further change if I drive for several hours. Tried covering coolant radiator, no help. Old anti-freeze looked like new when it was changed. Had heater apart and all manual controls and pneumatic valves function normal. Am I the only one having this problem and is there a fix?
the blend door could not be all the way to the hot side. if i remember right it's run by a cable, maybe not on the 98. anyways even if the actuators/cables are working properly the door may still be broke. its a possibility
The heater is in a plastic or fiberglass sealed enclosure but I was able to check all of the doors, actuators, and cables by using an inspection mirror and they are all OK and functioning properly. I wonder if something might be restricting the coolant flow to the heater radiator? I have also thought about putting an auxiliary electric pump in the heater inlet tube. They are steel tubes so it would be a job. I really wonder if something is restricting the coolant flow to the heater.
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