Switching From Dash Vents To Demister Vents When Under Power.

[BOR15]

in my VX i thought it was an actuator. When i was testing the double actuators, i found it didnt hold vacuum. What i discovered is that the 2 hoses are linked so you need to block the second when applying vacuum. All actuators passed the test.

 

[Immortality]

You could try removing the vac module and cleaning out the actuators. It's not that difficult. you'll see which one is used the most as it will have the dirtiest patch on the foam filter covering the various actuators. They can be cleaned out however I believe the rubber tips also wear out where they seal inside the actuator.

 

[BlackoutSteve]

Update.. In my case, yes it has turned out to be the solenoid pack. 3 of the 5 solenoids leak on my Caprice's unit, which is located below the glovebox.
One reason why it's hard to troubleshoot this item is that the foam dust filter pad does a really good job of muffling any hissing vacuum leak/s, and using a vacuum gauge won't help much because it's the atmospheric side of the solenoids that leak.

After checking the illustration below (thanks BOR15) I tried to clean the internals of the solenoids with WD-40, then blasting with compressed air. That didn't work so I then tried carb cleaner and that failed also. You may have more luck but I noted no change.
Temporarily mounted, the hissing from the solenoids (one at a time depending on mode) was quite audible.
To double check it was this leaking causing the AC to default to hot-demist under sustained engine load/low manifold vacuum, I simply plugged the leaky solenoids with Plasticine and went for a drive. Not once did it default to hot-demist from cold-face.

Thanks BOR15 for posting this image..

For VT models, the aftermarket unit part number is SE2420 and is about $70 from CoolDrive, however, this is not the same as WH (& Calais??) which actually uses the 5-solenoid VN-VS unit, CoolDrive part number SE0644.
The problem is that SE0644, aka GM Delco 16050460 and the superseding GM Delco 16171742 have all been discontinued. ..in Australia
However, here is the Google search 16171742 result https://www.google.com/search?q=161...=UeisVMWNMZPn8AXOuYDoAg&ved=0CAcQ_AUoAA&dpr=1
and the eBay USA result, also using the new Delco number. 16171742 | eBay
A description finds this locally. VN VP Berlina Calais Statesman Caprice AC Heater Vacuum Solenoid Block NEW | eBay
However, I just bought a pair of Delco 1617142 from Amazon, landed for just under AU$150. Now waiting on the postman..

 

[Immortality]

Yep, those are the buggers. I purchased a brand new one from the US about 2 years ago fairly cheap, I did put a link up to the supplier in another thread but I can't remember where it is

Good to see you finally got it sorted.

 

[Tuffin89]

Hey. New here. Not sure if I should start a new thread or not ... I've read everything I can about vacuum leaks on Just Commodores - but all these tips haven't solved the problem.

Very similar issue but in my '98 vs 5L.

Idle WILL NOT drop below 1000rpm and under power the air con changes from face to feet but even if I remove (and block) the vacuum supply to the vent controller the idle still won't drop below 1000.

Hoping someone can help

 

[BlackoutSteve]

I'd be looking for another vacuum leak around the engine.
See if the idle changes when a can of carb cleaner is sprayed at gaskets, hoses and other areas where leaks are possible. That will indicate a leak.
Also, the usual system default when the A/C looses vacuum is hot-demist.
Perhaps there is another issue that still could be the solenoid pack, like a solenoid sticking perhaps.

 

[Tuffin89]

Thanks for that. I'll try the carby cleaner trick.

Has anyone ever tried pressurising the air intake instead? The old soapy water trick ...

 

[BlackoutSteve]

This is where it got confusing, but regardless, I have ultimately "fixed" this problem in a way that costs practically nothing..
The two brand new, identical Delco solenoid packs arrived and I replaced the assumed faulty unit with one of them.
The problem of switching vents that the Plasticine fixed returned immediately.
I figured I had been sent a faulty unit so I swapped in the other brand new Delco unit and same problem existed.
Both units bleed air from the vent at the rear of #3, 4 & 5 solenoids during different modes.

The fix..
A 3/4" length of electrical/pvc tape over the rear of the #4 solenoid. This prevents that solenoid leaking vacuum during "face mode".
Open up the black plastic case and put the tape over the port in the same way I Plasticined in the above pic.
Bear in mind that this is the solenoid pack of a WH.
On a VT or other model, open up the black case, remove the solenoid pack, reconnect the hoses and connector and start the car with the A/C on and in "face mode".
With your finger, find out which of the solenoids is leaking. Tape it, reinstall, and hopefully happy days.

As for the real fault/s? Maybe it's an actuator, or something else.
Anyway, I have decided that I don't care as the problem is fixed, and I am certainly not about to embark on the nightmarish job of pulling the dash apart and swapping about $250-300 bucks worth of parts that are probably not faulty either, only to learn that it's still something else.

Chances are your solenoid pack is fine.
Good luck.

IF buy chance your solenoid pack is actually faulty and you have a VN-VS, or a WH and need a new pack.
I bought 2 on Amazon landed for AU$150.
Yes they are the same with the new having a superseded part number.

 

[trevasty]

I literally made an account just to ask you about this...
My 2000 WH Caprice 5.7 has just had a new compressor, re-gas and dryer installed by my auto sparky. I asked him to take a look at my why my dash vents weren't blowing air while he was there, sadly he couldn't figure it out.

He thought it might be this part above, but he said he wasn't sure so I didn't commit the extra $150 haha.

I had a look at mine and tried to get it off, but I can't see any screws or clips holding it on. Could you link me to something that might show me how to get in there and get it off by any chance?

 

[BlackoutSteve]

Some knob jockey in their infinite wisdom has designed the heaterbox so the solenoid pack is mounted with two Philips head screws almost hard up against the firewall.
I used a Philips bit in a 1/4" socket along with many choice curse words that seemed to aid removal.

You may be able to unclip the rear of the case to reveal the solenoids without actually removing it. Try that.
See rhe images I have posted. Can you see the two clips on the top of the case thay allow the "door" to drop down? A standard screwdriver should help you unclip the tabs.
If you do need a new pack, both GM and the aftermarket have discontinuwd them locally, but I have two from the USA. PM me if...