2005 Buick La Crosse

Heater problem
2005 Buick La Crosse 6 cyl Front Wheel Drive Automatic 48000 miles

Have just noticed the problem, since it hasn't been that cold in Georgia. Have done some extensive research on AllData. There is no control valve for the heater core that I can find. The upper supply hose is quite hot, but the lower one is fairly cool. IF I turn the HVAC system off completely, the lower hose heats right up. As soon as I turn the system on, it tries to blow hot air for a few seconds, goes basically lukewarm, and then I notice that the lower hose goes cool. I have pulled the HVAC/ECACs fuse and done the reset procedure. As near as I can tell, the control actuators seem to be moving as I change temp settings. It is almost as if the heater core has become clogged. Could this possibly be?

January 18, 2009.

Both of the heater hoses should be equally hot if the heater core is not clogged-up-did you check the thermostat?

Jan 18, 2009.