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A/C controls acting up

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Burbinator, Oct 19, 2001.

  1. Burbinator

    Burbinator 1/2 ton status

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    On my '91, the A/C compressor cycles like the A/C is on when the selector is off, vent acts like A/C, etc. The vacuum actuators are working properly (i.e. "max", "norm", "bi-level", etc. Air is being directed to the proper vents) and the temp selector operates as normal. Here's the part that concerns me : I can detect a burning smell and saw a little smoke come out of my dash briefly. I haven't torn apart my dash to check out the controls yet and was hoping someone either had the same problem at one point or could give me some direction. Thanks in advance!

    The learning curve is a toll road...ride with someone who has already paid!
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  2. Burbinator

    Burbinator 1/2 ton status

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    Problem solved. I took the dash apart and found a piece of foil gum wrapper in the control preventing it from totally shutting off. The current draw was enough to make it smolder a little. It looks like someone folded this foil piece and put it on the A/C vent bottom to compensate for its looseness. Good thing that foil didn't catch on fire!

    The learning curve is a toll road...ride with someone who has already paid!
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  3. Blue85

    Blue85 Troll Premium Member

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    Glad to hear that you figured it out. I was going to say that your problem is in the electrical switch in the heat/A/C control panel. The selector slider is actually connected to two switches. One is a vacuum switch to drive all of the vacuum motors that direct the airflow. The other is an electrical swith. That switch has two functions. First it applies power to the fan setting switch so that current flows through the switch and through one of the resistors and through the fan motor. The second function is to turn the A/C compressor on and off (it is on for all settings except "heat" and "vent", according to it's normal cycling operation). The two functions are from two tracks inside what is sort of a rotary switch. Sometimes that switch wears out a little bit and lets the contact touch in the vent position. You can replace it or take the switch apart and put some epoxy in the spot. The spot should be obvious because there will be signs of arcing around it.

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