Blower motor resistor wiring help?

Heating / Cooling / AC

  1. Johnny Mac

    Johnny Mac www.blueprintengines.com FABO Vendor

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    Hello all,
    Please and thanks in advance.
    Heater box is from a 78 charger. I am puzzled by how to wire in a universal 4 position blower speed switch.

    Resistor is shown.

    Cannot find a wiring diagram newer than 76. It does not match.

    On RH plug.
    Top (brown w yellow) runs to nothing. Just a female butt.

    Middle RH(bright green) runs to OE speed switch.

    Bottom RH (black) also runs to OE speed switch

    Left upper (tan) runs to OE speed switch, bit also appears ran to a 12v fuse on fuse box.

    Left bottom (green w white) runs to a stripped end.

    Blower motor hot appears to be green with no tracer

    I'm a little lost on this one...any advice?

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  2. Johnny Mac

    Johnny Mac www.blueprintengines.com FABO Vendor

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    Screenshot_20200625-202221_Samsung Internet.jpg
    Dug this up...but still a few extras to wrap my head around

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  3. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    Get out your ohmeter. ID and mark the blower and power (feeding the switch) leads.

    The resistor to switch leads should be open that is they only go from resistor to switch, so with these unhooked at both ends they should show no continuity to anything else, or ground.

    I'd wire it up with "clip leads" and mark what is hi, med, low using the motor, resistor, and battery.

    This is a "wish I was there" thing
     
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    • Johnny Mac

      Johnny Mac www.blueprintengines.com FABO Vendor

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      Yeah I thought I was going to simplify things with a universal harness, and universal switch....famous last words.
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      Thing is, you might be overthinking...........

      There is one power feeding the switch..............and one output, the blower motor and to ground

      The switch simply selects which section(s) of the resistor. It might be depending on how your universal switch is set up that you cannot make use of all sections of the resistor. Without an OEM diagram, that's why you need to "clip lead" it and figure out what the resistor is doing

      It appears to me that all resistors are common at the one end, and the three terminals on the other end would then be the various speeds.
       
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      • Jimacuda

        Jimacuda Well-Known Member

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        Looks very much like a 77-78 aspen/volare w ac piece.
        Same offset mtg holes. By 79 they were even.
        F,M,J and late B bodies have a lot in common.
         
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