Jeff®

She has an 88 Safari. The air vents only shoot air out the defroster. It's a rotary type switch and I believe the air duct diverters are motor driven. The fain and air compressor clearly work. When I change the vent outputs, nothing changes. The air comes out the defroster, and I don't hear the motor that switches vents anymore. I checked all the fuses, under hoo and under dash.

Any ideas?

Cajun

I have had a bad switch do this...more than once...different cars.

Cajun

hhrcrafty

The dampers use vacuum diaphragms to flip the doors between modes. The system defaults to defrost and floor for safety purposes if the diaphragms fail. Chances are one or all of them are leaking and you'll have to do some digging under the panel or drop the whole IP to find the bad ones. Few dollars in parts for a lot of hassle. Same thing happened on my Dad's old S-10.

jeffs396

Jeff...what I want to know is...how is it that you are driving a 2008, she's driving a 1988??? That's just not typical in today's society! Seriously though, crafty is correct, but you may get lucky & find a vacuum LINE bad to one of the actuators...you can test the diaphrams with an inexpensive vacuum pump also. Could also be the vacuum selector switch. It's just NO fun working under the dash, but that van may not be too bad. I had an 86 Astro years ago, underdash access wasn't bad at all.

Jeff®

OK, thanks. I didn't think of a vacuum line. are they operated by a solenoid perhaps?



As far as the model years go. Uh hem. I was driving a 93 Ranger with 208K on it. (still have it). I drive 70 miles a day and it started costing over $250 a month in gas. We needed a better milage car for my commute, and she's not working right now. Interesting how that new car turned out to be an SS.

She gets to drive it.

hhrcrafty

Nope. Those old selector levers were vacuum mechanical. Ever notice how if you switch from A/C to heat (if I remember correctly) on the old cars with the engine turned off you'd hear a whoosh of air and the door closing in the doghouse? That's the residual pressure being bled off.

If you want to save some time, you can always get one of those little 12v clamp-on fans and use it to scavenge the air off the floor and direct it up to your face...

-md- HHR

He is 100% correct.

ZTony8

Or you have a bad mode switch.

ChevyMgr

Or a bad vacuum canister. The vacuum lines on this vehicle are a nightmare. Get ready for some labor intensive searching if its a hole in a line.

Doc brown

I vote for a bad mode switch. Those were essentially the same setup on GMs from the early '70s well into the early '90s. I replaced several of the switch units on '70s and '80s GMs that I owned for exactly the same problem. One thing to check is to pull out the switch unit and see if it smells burnt. You might even see evidence of burning on the switch contacts. You can also probably pick one up cheap from a bone yard and put it in just to see if that fixes the problem.