Questions and Answers

Chevy Astro Van A/C Out Of Control Q. I have a 1998 Chevy Astro Van. 72,000 on odometer. A/C compressor runs and is cold. Fan blower runs in all 4 switch positions. There seems to to a vacuum problem and I can not find the cause. The selector switch has no effect on changing what duct air comes out of and I cannot get air to the dash ducts at all.

I have disassembled the entire dash and found that the blades that control ducting are not being actuated by vacuum to move them. The diaphragms seem okay as I can manually blow in them and they work. There just isn't any vacuum in the lines it seems.

Is it the selector switch or something else? I am lost. All fuses and relays are okay, checked by substituting them and now I don't know where to check for a vacuum problem. No other problems noted in vehicle and this just came on suddenly without prior warning.

Thank You so much for any advice you may offer.
TH

A. The vacuum you are missing comes in from under the hood. I've seen this problem before. Try looking at the left side of engine when looking under the hood. Down under the alternator there is a vacuum storage canister, kind of hard to see. There should be a hose on it that goes to the intake manifold and tees off to feed the HVAC. It's probably rotted from heat near the alternator and will need to be spliced. This canister is bolted to the frame rail and is a round black plastic softball sized thing.