Want to be

Quick question - vacuum line.

Is the vacuum line constant? If not - how does the control valve work and it's purpose.

Thanks for info and help

Eplebnista

vacuum is sent to the valve when the heater is turned on. Not constant.

Want to be

Thanks for the info. This would explain why the heat is on during AC.

Note- I've replaced the valve and redid the vacuum lines a while back.

Question # 2

How can I find the correct vacuum line?

Where is the vacuum line located? I don't think any of the map charts I've seen display the location of the vacuum line.

Thanks again

Ducman82

Should be the only one hanging out back there.

Want to be

I'd pulled every vacuum line a year ago. I'd assume I've spliced it with another line while replacing the vacuum lines.

Ducman82

It should be a stand alone from the center console. I wanna say white

Want to be

Ahhhhhh. I'll check tonight after the grand prix.

dr bob

Otto may be steering you wrong.

The heater control valve fails to the "open" position when no vacuum is applied. So vacuum will close the valve when there is no demand for heat. The solenoid for the heater valve is activated by contacts in the "setting motor", a servo-and-switch device that also directly adjusts position of a flap in the system that blends heated and cooled air based on control settings and interior temperature.

By far the most common cause for heater valve "stuck" in the open position include vacuum leaks in the other actuators in the system. Those leaks reduce the amount of vacuum available to other devices including the heater valve. There are several good troubleshooting procedures available here with the search function. All require you to use a hand vacuum pump like a MitiVac or similar to test each of the actuators individually from the center console solenoid bank. I found a good hand pump at Harbor Freight, identical to the Craftsman kit that I own except for the stickers, and half the cost.

Find and fix the leak, and it's quite likely the heater valve will then be able to close when you run the AC.

FWIW, many in warmer summer climates choose to use a small tie-wrap to hold the heater valve completely closed during AC season. This will temporarily mask the problems caused by vacuum leaks in the system, and also reduce the recovery time needed to cool a heat-soaked car on a hot day.