I have a GTA with digital dash and pushbutton style hvac controls. My vents haven't been working properly and I've narrowed it down to a problem with the vacuum control module.

Each vacuum line to a door actuator either has vacuum applied or is vented (so the vacuum is released). Thing is though, that looking at this unit I can't figure out how that is meant to work, because when any one of these lines is vented, there is a vacuum leak. Ie, if I plug all the ports except the input one, I should be able to produce a vacuum on the input line, right? The only way that would work is if all 4 solenoids were engaged.

I disconnected the input vacuum lines from the black valve you can see in the picture, and tested the solenoids. Each one works properly and you can hear a click when 12v is applied... it then holds vacuum, or if you block one of the lines to it and blow into the other, it is sealed (no air is vented out).

So basically this thing just produces a vacuum leak through any solenoid that isn't engaged. Does anyone know how it is meant to work?

The only thing I can think of is that maybe each solenoid has an internal spring which is either gummed up or has weakened... and the internal piston or whatever isn't moving back far enough to vent only the "out" line, not the "in" line. In which case maybe a squirt of wd40 through each one might help.

Any ideas?

 

Got it figured out... it needs gravity... duh As long as it is mounted vertically it isn't a problem, and the inside valve pieces block the input lines so there's no vacuum leak.

My car has been converted to right hand drive though which means the heater box has been relocated to the left, upside down. This module was mounted on top of it, on the part where it's at 45 degrees... that explains why it would only work sometimes (if I was somewhere gravity is that little bit stronger perhaps?!)

I'll figure out a better way to reinstall it so that it's vertical and hopefully there'll be no more problems. But just in case, if anyone has one for sale lemme know.