I have no vacuum signal at the heater control valve.

[Maleficio]

I wonder why?

I replaced the valve today, but discovered my original valve was still good, I just have no vacuum there. Checked for vacuum at the test port by the brake booster, barely had a signal there.

Any advice on a likely culprit?

[MPDano]

I bet it's leaking at those solenoid row thingys behind the Center Console. I tested my Euro all the way there and that's where my leak was. I just routed all time vacuum to my heater control valve till I can source a used one. Just not a priority right now.

[76FJ55]

It's also some what common to have the vac line come loose in the engine bay by the brake booster. IIRC there is a line that comes off the check valve looking piece, that then goes to what looks like a 4 way connector (but the 4th is blocked) which should have 3 lines connected to it. If one of these lines is disconnected you'll get no vac at the hvac control block.

[Maleficio]

Originally Posted by 76FJ55

It's also some what common to have the vac line come loose in the engine bay by the brake booster. IIRC there is a line that comes off the check valve looking piece, that then goes to what looks like a 4 way connector (but the 4th is blocked) which should have 3 lines connected to it. If one of these lines is disconnected you'll get no vac at the hvac control block.

My setup is intact. That fourth port is for testing vacuum pressure.

[Maleficio]

Originally Posted by MPDano

I bet it's leaking at those solenoid row thingys behind the Center Console. I tested my Euro all the way there and that's where my leak was. I just routed all time vacuum to my heater control valve till I can source a used one. Just not a priority right now.

That's exactly what I was thinking about doing. Where'd you source the signal?

[rjm65]

Maybe a collapsed vacuum line someplace between the 4 way and the vacuum port on the throttle body. Those are hard to track as they look ok from the outside, and the weak/bad area might be well covered up.

[Sapientoni]

The bank of vacuum valves for all the climate control doors have a foam "filter" that deteriorates with time and the slightest crumb from them is sucked into the valve, then you have no vacuum because all of them are probably leaking and there's only the one 4 x 2 mm supply line going to the whole bank and 4 or 5 leaking spots.

[Mrmerlin]

go to 928gt.com and under tips and links find Wallys guide to HVAC system diagnosis there you will find how to test the system , my guess is that you have one or more failed vacuum pods under the console thus they leak and thus you dont get full vacuum in the system to shut off or open the various selected

[stepson]

Is the blue check valve by the brake booster installed in the correct position? It may be backwards. Been there, done that.

[Maleficio]

Thanks for the advice, guys.