Heater Valve T1N (02-06)
This heater valve opens and closes to allow hot engine coolant to flow into the heater core in the dashboard which provides heat for the cabin. It opens when you want warm air and closes when the AC button is pushed.
*It requires power to stay closed*
This means that if you remove the climate control module/head unit for repair or replacment (or it is malfunctioning), this valve will stay open: Hot air will blow.
This heater valve is easy to locate and replace. It is located in the engine bay, on the passenger side of the van, above the turbo.
Testing it is easy, too. Use a 12v source to apply power to it. You should hear a "click" as you touch the live wires to the heater terminals and as you remove them.
If you do not hear a clicking, the valve is bad and should be replaced.