My center vents will only blow cold air instead of warm about 50% of the time. I have concluded that this isn't the fault of the heater valve, as I can get hot air out of the defroster at the same time as the face vents are blowing cold. I suspect the hot/cold thumbwheel between the vents is causing the problem, as documented on.... somebodys website. It seems that the thumbwheel moves a varible resistor that tells the HVAC whether to send warm air to the center vents, or cold fresh air. Several times I have heard a flap-closing sound seconds before icy air starts blowing out of the vents. I suspect this variable resistor has an intermittant fault that gives a high resistance to the IHKA.

My idea is... Simply bypassing the varible resistor with a wire, thus telling the IHKA that the thumbwheel is always set to red, meaning that the air coming out of the center vents was always just as the temp controls were set at.

Anyone see a problem with this? Other than not being able to have cold center-level air at the same time as hot air elsewhere.