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HVAC Selector Dysfunction


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The HVAC control cluster on my Loyale Sedan Ash doesn't seem to be able to select the heating to the windshield with any regularity. I can turn on the blower full speed and the hit the top button for the windshield and it doesn't change from blowing through the front vent outlets. I have seen this happen before where the vacuum line from the engine to the storage tank becomes unhooked. But it is connected and the lines look good. I even tried replacing the vacuum tank with one from the junkyard but that didn't make it any better.  If I press the heat button and fiddle with the blower speed from low to high a few times, the mechanism starts to divert the air to the floor at which point I "fake it out" and quickly switch to to windshield button and then air comes out on top as it should. I was doing a lot of that during the xmas tree run while trying to drive in the snow. I would like to make this so it doesn't require any fiddling. I am pretty sure it is either a vacuum leak in the hosing system or a lubrication issue.

 

My hunch is that there is a mechanism that is in need of lubrication. I only say this because the car is 22 yrs old, spent most of its life in Eastern Washington and all the other fixes (master window switch, power door locks and window roller channels) all involved cleaning and lubrication.  Has anyone else dealt with this issue?

Edited by MR_Loyale
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The "cables" that the selector switch move are a push style. They crack and slip out of the housing making it very difficult to move the flapper doors. I would check them first. Maybe you can repair them with a sleeve if they arent too gone. Some lube in the housings might help too.

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May want to remove the control unit from the dash mainly to get a look at the back of it.

 

Really sounds like what my Wagon was doing after I got it all back together and running.

Had to play around with the buttons to get it to change modes. Found that if I left the screw out that hold it to the dash, it would work, sort of.

 

Finally pulled it out of the dash completely, found the back of it was broke into several pieces.

Swapped in the control from the parts wagon and all is good.

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I just went through this on my 1988 DL. I ended up replacing the vacuum control unit (mode selector switch) in the dash with a lower mileage part from the junkyard. So far it is working great and switches modes right away now. Sometimes it would take an age to go in to defrost. I'll caution you not to loose the small rubber/plastic vacuum cap like thing on the rear of the control unit where it fits into the receiving hole in the dash. This is what helps snap off the tiny upper screw tab on the dash bezel. Also the selector cable is often routed on the wrong side of the radio braket causing an undo side load which also brakes the dash. Caution and attention to detail really pays off here.

Edited by Crazyeights
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