VX climate control vacuum leak

[RustyNS]

Hello All.
Can anyone give me some ideas on troubleshooting a vacuum leak in my VX SII Berlina Climate Control AC controls? It does the thing where when accelerating the vents change from blowing the air through the dash vents to blowing onto the windscreen and then back to the dash vents when backing off and getting good vacuum again. I've searched and read it referenced to, but not found any solutions yet.
I currently have most of the dash out as I am going to wash out the evaporator tomorrow, but would like to have it all back in again by tomorrow night.
I have checked the vacuum hose out of the back of the intake plenum and it is good - still flexible and no splits. I've checked the check valve there too - works correctly and no leaks. I've looked at as much of the hoses and control block etc under the dash that I can get to and it all seems ok.
Any help will be appreciated.
Cheers, Rusty

 

[2O4TS]

Probably a vacuum solenoid. You have 3 options to direct the air, screen, face, feet. You know it goes to the screen so likely the solenoid that directs air to face or feet. When I upgraded to climate control the HVAC box obviously had one dodgy solenoid. If I set air direction to feet it stays there under acceleration. If I direct it to face it soon directs to screen under acceleration. Obviously the dodgy one is the face direction solenoid.
I will also being doing this in a couple of weeks when I replace my heater core and will test the solenoids etc. with a vacuum gauge but based on my test I'm pretty confident which solenoid is the problem.
If you have a vacuum pump with a gauge you can easily test every part of the system for vacuum leaks. Just keep an eye on the gauge. If the vacuum starts dropping you're narrowing down the specific issue.

 

[Dak]

Check the reservoir down below the LH headlight in the inner guard, they are known to crack.

 

[RustyNS]

Thanks for the replies. I have ordered a vacuum pump and gauge off ebay, pretty cheap, so I can test it when I get back to it.

Check the reservoir down below the LH headlight in the inner guard, they are known to crack.

I didn't know there was another reservoir down in the LH inner guard, will have to have a look at that too. Cheers.

 

[2O4TS]

Thanks for the replies. I have ordered a vacuum pump and gauge off ebay, pretty cheap, so I can test it when I get back to it.


I didn't know there was another reservoir down in the LH inner guard, will have to have a look at that too. Cheers.

The reservoir in the LHF inner guard is your coolant overflow reservoir and has SFA to do with your climate control.

 

[accentstencil]

I'm pretty sure that earlier models have the ball shaped tank behind the guard and your model has the tank attached to the heater box on the passenger's side.

 

[Dak]

The reservoir in the LHF inner guard is your coolant overflow reservoir and has SFA to do with your climate control.

See post below, they DO have a vacuum tank down in the LF guard, below the coolant reservoir.

 

[convas]

My VT was doing the same thing when I first bought it, in my case it was the vacuum solenoid, pretty easy to diagnose with a vacuum pump.

https://forums.justcommodores.com.a...ing-by-itself-98-vt-berlina-3-8-ltr-v6.91682/

 

[2O4TS]

See post below, they DO have a vacuum tank down in the LF guard, below the coolant reservoir.

Well I've worked on numerous VT's on since 2000 and I've never seen a vacuum reservoir inside the guard nor is there any mention of one in the GMH Service manual. Below is a pic of the vacuum schematics for ECC and a photo and description of the location of the vacuum reservoir straight out of the GMH Service Manual. As accentstencil posted above, the earlier models might have a vacuum reservoir in the guard but the VX that the OP refers to has the vacuum reservoir mounted to the passengers side of the HVAC unit.