heater valve?

[redhotrod]

I got a question pertaining to the heater.
My car comes up to temperature alright, has plenty of antifreeze but my heater/defrost blows cold. I noticed there is some sort of valve or something inline with the heater hoses. Why is it there, and how does it work? Does vacuum operate it? If it is defective, could I just cut it out and bypass it?

 

[mgmshar]

That valve is a heater water valve. It either allows or blocks coolant flow to the heater core, depending on where you have your climate control switch. The valve is operated by vacuum.

1. Put your climate control on "Heater", and slide the temperature switch to "Hot". Look carefully at the position of the actuator on the valve. This is the open position (allowing coolant to the heater core).
2. Put your climate control on "Max A/C", and slide the temperature switch to "Cold". Look again at the position of the actuator on the valve. You will see that is has moved. This is the "closed" position (blocking coolant to the heater core).

If I am reading the shop manual correctly, the only time vacuum is applied to the heater water valve is when the A/C is on "Max A/C" and the temperature switch is in the "Cold" position.

If the valve is not moving, you are either not getting vacuum to the line on the valve, or the valve is stuck. If the valve happens to be stuck in the closed position (not likely, but possible), then it needs to be replaced.

The other possibility is that the temperature door inside your climate control system is not moving when you slide the temperature switch. Can you hear/feel the door inside the unit moving when you slide the switch between "Cold" and "Hot"?

Good Luck,