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    Cruise control

    The cruise control doesn't work on my 85 Gm, you guys got any pointers as to where to start diag?

    #2
    Check for a binding cruise control cable and vacuum leaks first.
    What I Own: 1993 Mercury Grand Marquis GS
    What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

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      #3
      Check the cruise vacuum switch, pull off the line from the cruise servo that goes down and into the cab. It should hold vacuum, if it doesn't, try lifting or wiggling the brake pedal.

      You can also try lifting on the brake pedal why trying to engage cruise control while driving. There's also an electrical switch on the brake pedal that could've come out of adjustment.
      1985 Mercury Grand Marquis LS, "Maisa"
      1995 Chevrolet Caprice Classic STW, "Sally"

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        #4
        The vacuum line going to the automatic park brake release was capped off, would that effect the cruise?

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          #5
          nope. The vac dump valve is different plumbing.

          does the horn work? If not, the buttons for the cruise don't have any power and it won't work
          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

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            #6
            Originally posted by gadget73 View Post
            nope. The vac dump valve is different plumbing.

            does the horn work? If not, the buttons for the cruise don't have any power and it won't work
            Yes the horn does work

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              #7
              Does anyone have a diagram or anything for the cruise related vacuum/wiring?

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                #8
                Vacuum is simple, one line from the servo goes to the brake pedal switch and the other goes from the intake manifold vacuum tree to the servo.
                1985 Mercury Grand Marquis LS, "Maisa"
                1995 Chevrolet Caprice Classic STW, "Sally"

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                  #9
                  This is the section from my 84 Continental EVTM. Same system used through 1987 on the Panther cars but the connectors are probably numbered differently. Only real difference, the connection where it says 'from electronic instrument cluster' comes from the VSS. On the digital dash cars the VSS goes to the cluster first.

                  Click image for larger version  Name:	20230128_105107.jpg Views:	0 Size:	1.63 MB ID:	1385581 Click image for larger version  Name:	20230128_105128.jpg Views:	0 Size:	1.74 MB ID:	1385582

                  this is where I'll yet again mention that having an EVTM for your particular car is a really good idea. I've become something of a document hoarder, any time I find some sort of factory manual for one of my cars that I don't have, I buy it if the price isn't stupid. The EVTM and the body/chassis/electrical manuals are by far the most useful but I've ended up with full wiring diagrams, radio service manuals, and EEC/emissions diagnostic manuals that have been useful at various points.
                  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


                    #10
                    Originally posted by Arquemann View Post
                    Check the cruise vacuum switch, pull off the line from the cruise servo that goes down and into the cab. It should hold vacuum, if it doesn't, try lifting or wiggling the brake pedal.

                    You can also try lifting on the brake pedal why trying to engage cruise control while driving. There's also an electrical switch on the brake pedal that could've come out of adjustment.
                    well I’ve looked into it and it appears that the plastic tab that pushes the vacuum switch button is broken

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