My heater in my 2001 gmc Sierra will not blow any heat. My ac works foine blows

[cramsnomme]

cold air. Waterpump bad thi?
Heater core is warming up, coolant is not leakng, seems like some valve or something is not closing

 

[Aaron]

you may be low on coolant, which is a bad sign. or it could be that the valve which controls the amount of hot coolant going into the heater core is stuck closed, so only the cold coolant is stuck in there.

if your water pump is toast, it just leaks fluid out, but it still turns so it could be feasible that it is bad, but based off of no hot water in the heater core.

hope this helps.

 

[knuckleheaf27]

i have the same problem with my 01 sierra..... the thing about it is i will turn the heat off and let the truck get to its running temp, then turn on the heat... its hot for just a moment but then cools off.... its very frustrating, i just put a thermostat in last year and i cant figure out what the deal is.... its not low on coolant... im open for suggestions... thanks