Hey when my B4000 is cold, the temp gauge reads WAY below the cold mark. At operating temp, it has moved up just barely above the "C" about a needle's width. I'm wondering if maybe the needle had been moved at some point. I bought this truck used, and it looks as if the cluster lens had been removed. Grounded the sender wire, gauge goes full hot, sender is brand new. Also, my coolant temp at operating temp stays around 185-190, but my heater takes ridiculously long to heat up. I have to let it run for a good 45 minutes in the morning just to get the cab from 30 degrees to 45 degrees. Then after about 2 miles, it gets relatively toasty, but nothing like it should. I just need a few ideas I guess. Thanks

 

temp sensor - did you put teflon tape or sealer on the threads this would affect the grounding of the sensor as the engine warms up

long time to warm up heater core blocked/plugging up
have it flushed