My 92 d-350 has been running cold for a couple weeks. The temp gauge will barely lift off of c no matter how long i run it. And the heater wont work. I was thinkin it could be the thermostat or heater core?

 

Sounds like a stuck thermostat?

 

X2

 

That's exactly what that is. Replace it with a good thermostat and you will be warm and happy!

 

i agree with all the above

 

Ya know that the Thermo might just be the problem. But - did you also check the level in the radiator? If you happen to have a leak in the cooling system and loose antifreeze. A low coolant level will do the same thing.

 

Good point.

 

My water pump leaks so im constantly adding coolant. Im sure it is the thermostat but how much of a hassle will it be to change? On my blazer i can do it blind folded

 

you could have a short in the gauge thats what to me

 

if the heater was working then it might be a short in the guage, the temp sender dont effect the heating, change the t-stat and you should be good