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    HVAC Blower Speed Control Question

    Hello Friends,

    I'm having trouble with the HVAC blower motor control on my '94 MGM. The blower motor will only run on high speed on the "HIGH" setting or the "AUTO" setting.
    I suspect the blower motor resistor unit is out. I would like to bench test the unit before I get another one. Also, my Haynes manual is weak on the HVAC electrical diagram. Can anyone tell me what connector pins on the resistor unit to place an ohmmeter on and what the resistances should be?

    Thank you in advance,
    Mark in Indiana
    '94 MGM-LS
    Mark in Indiana

    1994 Mercury Grand Marquis LS

    #2
    I just had the EXACT same problem in mine, it was the resistor. The resistor sits in the plenum, just downstream of the AC core, behind the passenger valve cover. New they're $150, I found a couple good ones in the junkyard. There's a solder joint(s) that can come loose, and people have reported that resoldering them can fix the problem. For a while, mine was flat stuck in full auto, no off, and no high. Eventually, I got auto, off, and high back, but then I found a new resistor and life was grand. I found my resistors in Town Cars because EATC is so rare in CVs and GMs. There are 2 different resistors (plugs) and I don't know what makes one different than the other. I don't think in the ones I found that the year had anything to do with it.
    1992 CVLX. 5.0 HO/GT40P/T5/3.73/trak-lok with bolt ons. 02 front CVPI setup, rear HPP setup, CVPI shocks around, F250 radiator, e-fans, and the power of 3G. 15.92@89mph, 2.4 60', 4700' elevation (5500' DA) with 3.08 open rear and the old oil chugging 289. RIP.

    Comment


      #3
      The EATC isn't so much a resistor as its a control module. Pull it out and you'll see a circuit board, not just the standard coils like you'd find on a normal blower resistor. Usually re-soldering the connections on that type fixes it.
      86 Lincoln Town Car (Galactica).
      5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

      91 Lincoln Mark VII LSC grandpa spec white and cranberry

      1984 Lincoln Continental TurboDiesel - rolls coal

      Originally posted by phayzer5
      I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

      Comment


        #4
        BTW, I forgot to mention that the fan speed control switch is like a volume control on a radio. It doesn't "step" through the different speeds. I found a couple of my type of resistor blocks on some Town Cars at the J-Y today. Unfortunately, neither one of them worked. I'll dissect one of them and try to repair it. Assuming that the silver component on the PC board is a transistor, I should be able to cross reference it in a transistor characteristics book. That's the fun of an older car. Easy to find cheap parts at the u-pull J-Y.
        Mark in Indiana

        1994 Mercury Grand Marquis LS

        Comment


          #5
          yeah, its a big transistor. Usually where the power transistor leads solder to the board is the problem.
          86 Lincoln Town Car (Galactica).
          5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

          91 Lincoln Mark VII LSC grandpa spec white and cranberry

          1984 Lincoln Continental TurboDiesel - rolls coal

          Originally posted by phayzer5
          I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

          Comment

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