henryk8398

Good morning,

I've been noticing, on and off, that my A/C and vent are blowing air from the wrong places. Sometimes it will work fine, but it seems like more and more, the cold air is either going to the bottom duct (where the heat should be) or the defroster ducts. Sometimes if I play with the controls, I can get air to come from the dash.

I've read that this could be related to some kind of vacuum issue.

Any usual suspect areas to check?

Thanks in advance!

Lady72nRob71

My 86 sometimes does this. Either the controls are malfuntioning due to shrunken, dried, leaking rubber seals or the damper control motors are getting stuck.
I bet it is the former issue, as it makes more sense and the little motors are pretty reliable.

henryk8398

Thanks for the reply!

When you mean controls, do you mean this little bugger?

http://info.rockauto.com/getimage/ge...S/15-71389.jpg

Lady72nRob71

That looks like it. Compare it to yours and see if it matches.

On my car, when stuck in the wrong mode, there will be a constant soft hissing at the controls. Jiggling the handle makes the hissing stop and the correct mode to engage.

henryk8398

I will definitely check out that switch. Are there any other components that are prone to failure in this area? I plan on testing the vacuum motors and the vacuum ball under the hood as well.

I've heard that the vacuum line to the heater control is a problem area, too.

If I happen to have a leak in one of the plastic lines, can those be replaced with a like item or would I have to use rubber hose?

Lady72nRob71

Testing the vac motors is easy. Take of hose, put on 2' of new hose and suck on it. Motor should move smoothly. Do check the hard plastic line going from engine bay to controls. Check the rubber connectors, too. Breaks in it can be repaired by cutting out the damaged area and splicing with regular rubber hose. The hard plastic stuff is hard to find.

If all the hoses and motors are okay, then get the vacuum switch.

NorTown Olds

Hey Henry,
Did you get this annoyance fixed?? Looks like you got great advice. This IS indeed a common ailment w/ the 80s Full-Sized cars particularly! My '84 Does it some; I find if I turn the heater on, THEN go back to 'VENT' or AC then it blows out the normal vents again. My '81 Ninety-Eight does this too and it's been in the Family since Day One and is a Low-Mileage Cream Puff!

GOOD luck and keep us posted!

John

henryk8398

Haven't been out in the garage yet. I'm going to go ahead and order the vacuum control switch in the next day or two. I'll post once I replace it!

Thanks for everyone's help!

Rickman48

Guess they used the same basic thing for a lotta years - I just replaced it on my '92 S-10 Blazer!
Got the whole control for $15 at a yard.

NorTown Olds

Yeah, guess so -- GM was pretty good about re-utilizing parts for years and YEARS on all kinds of their vehicles. Kinda handy for us Restoration and Preservation Types! (The Cross-Reference Manuals can be kind of fun to read actually.) Thanks for chiming in and GOOD find on that part out of a yard! (Do they still have those near Joliet?? Many in the Midwest are drying up due to overly aggressive EPA tactics...

henryk8398

Well, I finally replaced both valves behind the controller with brand new Delco parts. Everything seems great! Thanks for everyone's help!

Lady72nRob71

Where did you get the Delco parts? I need to get a set for my '86 before they break completely.

henryk8398

Amazon.com

I think I looked up the part on either Rockauto or Kayauto (a Delco dist.).

henryk8398

Rob,

I went to rockauto. Go the the listing for your car, select "Heat and Air Conditioning", then select A/C Vacuum Control valve. You will find 2 parts:

ACDELCO Part # 157975 {#07897420, 7897420}
VALVE,HTR & A/C CONT VAC 2 PORTS



ACDELCO Part # 1571389 {#16037778}
VALVE,HTR & A/C CONT VAC 9 PORTS
You will likely need both (the mount to the a/c-heat controls on the back). Check your application, I looked for yours as a 1986 Cutlass Supreme with a 307.

Good luck and thanks for all your help!