Need help with heat

[Firepuppy]

i have a 2002 expo and when im at idle the truck blows cold air only when i drive down road does it blow warm air not hot but warm i just changed thermostat today still the same i was told it was the water pump getting weak and not pushing enough water until under power is this possible
thanks

 

[docraymund]

Heater core might need replacing. Get hold of a repair manual for the procedure.

 

[98EXPnSRQ]

Sounds like your blend door might be broken. Make sure it is moving properly.

 

[walnuts4x4]

+1 for blend door... Very common problem

Back when I had my expy had this problem... I removed glove box and cut into the "box" that holds the blend door and I just taped the blend door to either hot or cold depending on season... Then sealed the door by using the heat tape that's used for household heating the aluminum tape... I only cut 3 sides and bent it up.... Ghetto, yes... But worked for me until I traded it in 3 years later...lol

 

[rtbrjason]

If it's warm while driving and cold while idling it's likely not the blend door. I think your heater core is partially plugged. You can disconnect the hoses and try blowing it out with a hose and/or some compressed air.

 

[gasouthernboy78]

If you pull the blend door actuator, take it in with you to the store. don't make 3 trips like I did haha.