Problem with Vacuum Air Diverter Valve
Thread Starter
3rd Gear
Joined: Jul 2008
Posts: 3
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Problem with Vacuum Air Diverter Valve
I have a 1985 C4 and I'm trying to determine which part or parts that I need to replace in order to fix my problem with the heat+A/C air diverter. The air volume from the blower motor diverts to the proper vents at low RPM. Once I accelerate and bring the RPM and vacuum up all the air moves to the windshield area or defrost. I called chevrolet and all the parts have been discontinued for this problem. GM part #'s 1996717-Defrost Vacuum Valve Actuator, 1996718-Diverter Valve acuator, 1996719-Valve Front & 1996720-Valve Rear. Also they listed a Heat + A/C check Valve. Does anyone know exactly which part or parts I need and where can I get them? Also in manual pics of this would be great. Thanks... Mike
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Check hoses at and the Vacuum Tank in the left head light well. The tank should hold 10 ins. if you suck it down with a tester. It's there to supply vacuum under the conditions you describe - none of the other stuff should have anything to do with it.
Thread Starter
3rd Gear
Joined: Jul 2008
Posts: 3
Likes: 0
Thanks, It may very well be the vacuum tank in the driver's side headlight area. I just got a C4 and this is my first Corvette and I don't have a clue about parts that are unique to the Vetts. My step son hit a deer about a month ago and it completely ripped out the headlight assembly. I've since replaced the headlight assembly, motor and never thought to check for any other broken parts like vacuum tanks or other canisters. I'll try this first. Thanks for you quick replies. I have three f-Body 3rd Gen Camaros and bring a lot of knowledge on L98 & TPI parts, just
Safety Car
Joined: Jul 2004
Posts: 3,835
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Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
All cars have vacuum tanks - well except maybe a Yugo since there's no a/c or cruise. The Vette sticks it in the headlight well - trucks are usually on the rear of the hood - the F and G Bodys sometimes hide them below the front of the left/right fender.
Intermediate
Joined: May 2002
Posts: 41
Likes: 0
From: Tampa Florida
Similar Prob
I think I have a similar problem. When I turn on the A/C (i.e. everyday all day down here in FLA.) The A/C only blows out the Defrost vent and fogs up the windshield (outside.) Nothing blows out the other vents. Does anyone know if there are any instructions (maybe with a photo or two) for the wrench impaired. I have a feeling it is the vacuum and I'd like to check it out, but I'm not sure what to look for.
Thanks
Thanks
