Vent Control Problem

My 2004 Chevy Astro is having trouble with the vent controls. It will not blow from the main passenger cooling vents. I can select the heater (foot) vents and turn them off. The dash defrost vent will always be on (unless I turn everything off). The air conditioning turns on and off. But no matter what position I select on the dial, I get no vent right on me.

I'm doing okay with the air conditioner on and blowing at my feet and defrost. But now it's summer in California, and this is not ideal.

Help on how to troubleshoot and fix this!

What controls the vents ? Many are vacuum operated.

there is probably a servo motor that switches the vent. those can go bad, but sometimes the selector door can fall out of where it's supposed to sit and jam up.

i don't know how hard it is to do on an Astro, but i fixed a 95 Suburban a couple of months ago by putting a zip tie on the door pivot to keep it from sliding out of position.

No specific knowledge, but a lot of modern cars use stepper motors. I had what is apparently a common problem with my old Saab 9-5 wherein the linkage between one of the motors and the flap broke (thankfully this was cheaply fixable with some PVC pipe and epoxy). What I took away from this experience was that, without very specific instructions from either a manual or some helpful Intarweb presence, modern ventilation systems are nigh on incomprehensible, though the repairs themselves can be relatively simple.

Not sure about the Astro, but I just had this problem in my 97 E150. Turned out to be a broken vacuum line from the intake to the AC control panel.

iceracer wrote: What controls the vents ? Many are vacuum operated.

I believe they are vacuum operated. I pulled off the front of the dashboard, and the selector seems to use a series of small air hoses. I'm not sure what they operate though. I wouldn't be surprised if there's a mechanical door somewhere that they're trying to engage, but that is stuck. I have no idea where to look for or how to access that.

I do have a Hayne's manual, but I could not find any valuable information on where things are in the vent system.

Internet searching seems to point to cracked/rotting/loose vacuum lines near the vacuum accumulator. I'm not sure where to look for this.

There is a small hard plastic line that runs from the drivers side of the intake manifold to the firewall, and then on to the heater control. It will be in about 6 pieces. Replace with appropriatly sized rubber hose.

I hardly ever see that problem on Astro vans every single time one is in the shop.

Streetwiseguy wrote: There is a small hard plastic line that runs from the drivers side of the intake manifold to the firewall, and then on to the heater control. It will be in about 6 pieces. Replace with appropriatly sized rubber hose.

Will this be something accessed through the top of the engine? Or from underneath? Course, you did say intake manifold, so I'm guessing probably on top... but I've had a few beers.

Closer to the front of the engine bay or middle/back?

I hardly ever see that problem on Astro vans every single time one is in the shop.

Do I detect sarcasm?

Salanis wrote: ... I do have a Hayne's manual, but I could not find any valuable information on where things are in the vent system.

Asking the GRM forums is usually quicker, but your local library might be able to answer your question too. Mine has factory service manuals for all cars/trucks from the Detroit 3 automakers from last year back to the early 70s. They don't have anything for imports though.

Bob

Schmidlap wrote: Asking the GRM forums is usually quicker, but your local library might be able to answer your question too. Mine has factory service manuals for all cars/trucks from the Detroit 3 automakers from last year back to the early 70s. They don't have anything for imports though.

Yeah, I figured there'd be some good specific knowledge here. My local library has the Chilton's and Hayne's manuals, but not factory manual.

Salanis wrote:

Streetwiseguy wrote: There is a small hard plastic line that runs from the drivers side of the intake manifold to the firewall, and then on to the heater control. It will be in about 6 pieces. Replace with appropriatly sized rubber hose.

Will this be something accessed through the top of the engine? Or from underneath? Course, you did say intake manifold, so I'm guessing probably on top... but I've had a few beers. Closer to the front of the engine bay or middle/back?

I hardly ever see that problem on Astro vans every single time one is in the shop.

Do I detect sarcasm?

Probably easier to lose the doghouse, but for sure the airbox has to come out. Its a bit buried, but once you find one end, its fairly straightforward.

As to the sarcasm, me? Never.

Streetwiseguy wrote: Probably easier to lose the doghouse, but for sure the airbox has to come out. Its a bit buried, but once you find one end, its fairly straightforward.

Doghouse?

Salanis wrote:

Streetwiseguy wrote: Probably easier to lose the doghouse, but for sure the airbox has to come out. Its a bit buried, but once you find one end, its fairly straightforward.

Doghouse?

Uh-oh. Language crisis-,What do you call the removeable cover inside the vehicle that allows you to see the engine on a van? That thing. We in upper Canuckistan always call it a doghouse.

Even here in the South, we call the cover a "doghouse".

In any case, you'll likely have to enter the deep, dark resesses of the dreaded "underdash" to find the vacuum connection. Not hard, labor-wise, but generally a PIA.

I had the same problem with my Astro. Mine had a broken plastic line that went across the top of the motor, from the driver's side of the intake manifold to the passenger side. I got at it by removing the doghouse. Any vacuum leak will affect your vents. Mine's acting up again,the vents don't blow when the throttle is pushed and I have less vacuum. Check all the vacuum linesuntil you find a leak.