1996 GMC Jimmy

Heater problem
1996 GMC Jimmy 6 cyl Four Wheel Drive Automatic 60000 miles

I replaced the thermastat but I still don't have heat. Once in awhile I get luke warm heat for a little while. Any ideals?
January 5, 2009.

I guess your blower works good on all speeds? After everything is warmed up and the hvac controls turned on, can you feel of the heater hoses under the hood, are they both hot?

Jan 5, 2009.
Yes the blower works on all speeds. The bottom hose is hot but the top one isn't.

Jan 5, 2009.
If you can feel air blowing out the vents, then you may need to flush your cooling system.

I did see a bulletin on this vehicle that uses dexcool. If the vehicle was driven a long time with low coolant level, it can cause a rust like substance to form in the coolant system, heater core included. Can you check for coolant flow through the heater core?

I just wanted to add, you might check the heater control valve where applicable.

Jan 6, 2009.