Hello all,

I am new to this forum and I have a 2002 h1 with a really luke warm heater in the front heater but the rear heater is quite warm. Any suggestions on what it could be?

Any help is appreciated.

 

i would check for a plugged or stuck water valve. it is mounted on the right side of the vehicle under the hood next to and down from the coolant bottle. it is a black valve with four hoses connected to it with a vacuum line going into the top of it. when the Hummer is running, look at the plunger on the valve with the heater on the plunger should be down, with the a/c on the plunger should be up. it is a plastic valve which is held to the side fire wall with a hose clamp, if the hose clamp is too tight the plunger gets stuck inside of the housing. if that all looks good than i would remove the valve and clean it.

 

mine is blowing warm then luck warm after it sounds like a switch flips under the dash. I will check the above valve and post what I find. 2007 H3 52k miles