90 Lumina 3.1 V6 - HVAC Vent Controls Inop

[90V6RedHotLuminaEuro]

Good Day!

 

The HVAC Vent Controls on my 90 Lumina V6/3.1 are inop. I just picked up the car recently and this is one of the problems it came with. The Fan control works, but only blows air through the Heater vents... I'm assuming the Heater vent is the Default vent. The Temperature control works. There is no Vent control/switching. Can anyone tell me where the Vacuum source for the HVAC controls connects up inside the engine compartment, what path it takes, and/or where the vacuum source enters the interior?

 

Also, at idle, what number should I be getting on a Vacuum Guage for a normal reading?

 

When I first got the car it had a Vac leak... I replaced a 3 way check valve and a hose to the reserve tank in the drivers side fender.

 

My Haines manual doesn't have schematics for the HVAC for my car... nor much of anything else regarding the system in general. I'm assuming the vents are controlled by an electronic vac solenoid bank of sorts.

Edited September 7, 2011 by 90V6RedHotLuminaEuro

[AL]

The vac hose you replaced is usually the one that goes bad and causes this... as you are talking about the one under the battery right

[90V6RedHotLuminaEuro]

The vac hose you replaced is usually the one that goes bad and causes this... as you are talking about the one under the battery right

 

Yep! I replaced that hose, which goes to the Vac reserve tank, and the 3 way check valve. The 3 way has a vac source coming from the engine, and then splits to the vac reserve tank, and the cruise control.

 

I'd like to know what path the Vac takes from engine to interior... to Vac Solenoids so I can trace it.

 

I'd also like to know what I should be reading for a Normal Vac reading on a Vac Guage.

Edited September 10, 2011 by 90V6RedHotLuminaEuro

[Schurkey]

On my '92 3.4L, there's a rubber elbow connecting to hard plastic vacuum tubing starting at the passenger rear corner of the intake manifold (actually connects to a nipple on the MAP sensor.) Plastic tubing melted from contact with the EGR tube. Tubing continues alongside master cylinder, under Cruise servo, behind battery and to the vacuum tank ahead of LF tire.

 

I cut out damaged (melted) section of hard plastic tubing, and spliced it back together with small diameter rubber vacuum hose.

 

This vacuum supply affects the HVAC and the cruise control.

[90V6RedHotLuminaEuro]

On my '92 3.4L, there's a rubber elbow connecting to hard plastic vacuum tubing starting at the passenger rear corner of the intake manifold (actually connects to a nipple on the MAP sensor.) Plastic tubing melted from contact with the EGR tube. Tubing continues alongside master cylinder, under Cruise servo, behind battery and to the vacuum tank ahead of LF tire.

 

I cut out damaged (melted) section of hard plastic tubing, and spliced it back together with small diameter rubber vacuum hose.

 

This vacuum supply affects the HVAC and the cruise control.

 

Thanks... your post got me digging again... but deeper... discovered some things... and FINALLY solved my problem.

 

First I did find a bad Vac connection... that would have gotten worse. It was at the Canister Purge Solenoid right next to the MAP Sensor. It's a rather thick Vac line that goes from the CPS under the Master Cylinder to a steel Vac Line that goes to the Charcoal Canister in the rear of the car. The hose end at the CPS was rotten/cracked. I fixed it but not sure if it was causing any issues since the overall Vac seemed Normal.

 

I still had no HVAC controls so I went under the dash to the Vacuum/Electric Solenoid. There's a Purple Vac line on it that is the Vac source. I bypassed it with a length of Vac Line coming straight from the throttle body. I wanted to test the electronics of the Dash controls. With the Vac source bypassed, the Dash controls worked. So I knew I was losing my Vac source somewhere. I was hoping it wasn't buried in the dash somewhere.

 

After much thoughtful hair pulling and tracing and Vac line pulling/rearranging. I finally found the little nubbin. It was under the Cruise Control Servo... a short piece of Vac line with an elbow on it... coming out of a taped up harness alongside and under the thick Vac hose that goes to the Cruise Servo and the Cruise/Brake release Valve.

 

So apparently, there was at one time, another "T" fitting to go with the Vac Line coming from the throttle body, to the 3 way check valve... the 3 way then splits to the Cruise Servo... to a "T" which then splits to the Vac Reserve Tank/Ball under the drivers side fender and to the HVAC controls. I added another fitting and everything works fine.

 

I rearranged and made more readily accessible all of my Vac lines. I pulled them all out from under the intake manifold... and now have visibility and access to all. Some day I'll inspect and investigate the Charcoal Canister... I hope the PCV is good... it's a real PITA to get to! ...I'm gonna pretend it's not there.

 

Thanks All... for all your help.

 

...Ok... let's see... what's next on my list... drivers side fender.... hmmm... salvage yard in Binghamton is probably still under water... gotta wait for the flood waters to subside... oh yeah... I could check all the dash lights since I got it all torn apart... and then... how 'bout motor and transaxial mounts... shouldn't be too difficult... bite my tongue... knock on wood... Ebay here I come!