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Speed control drops out after a feww sec when headlights are on.

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    Speed control drops out after a feww sec when headlights are on.

    Any ideas?
    84 Town Car.

    It must be electrical.

    Brake/turn signal light circuit had been modified to meet german laws that require a amber turn signal.
    The two bulbs per light assembly had been spearated into one for turn signal only and the other for park/brake by splicing the wires and runnig a separate brake wire to the lamps.

    Speed control did not work when I bought the car due to this modification. They had clipped and the green and green/red brake switch wires but they are mandatory for speed control operation. I traced that down to the switch wiring and after resoldering the wire I had speed control again.
    But only when headlights are off.

    I assume the dropping out of speed control after a few seconds of keeping must have something to do with the rear lights.

    #2
    Yah, I'm not an electrical guru but it seems as if they spliced or used the factory wire for the brake lights for whatever modification. So, when you turn your lights on the cruise module or whatever "sees" that the brakes are applied, thus killing cruise.
    1985 LTD Crown Victoria - SOLD
    1988 Town Car Signature - Current Party Barge

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      #3
      under dash grounds... if they're starting that insulation shrinking fraying business... that could be the issue. May also need to check the power lead to the cruise control module for the same issue.

      Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
      rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
      Originally posted by gadget73
      ... and it should all work like magic and unicorns and stuff.
      Originally posted by dmccaig
      Overhead, some poor bastards are flying in airplanes.

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        #4
        Check the grounds for your tail lights. The cruise control has to "see" ground through the brake lamps in order to be on. Thats why it drops out when you step on the brake. It doesn't actually look for +12v, it just looks for no ground. If the ground connection in the trunk for the lights (pretty sure its driver's side, near the trunk hinge) is bad, it will ground through the parking lamps if they are off. If the lamps are on, no ground, no cruise.
        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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          #5
          Thanks, I´ll check grounds.

          Comment


            #6
            I checked grounds. They are ok. Even cleaned them to be sure.

            I observed the following:
            When tail lights are ON and you look closely you can see the brake/turn light filaments to flicker very slightly. That´s why it drops out of speed control since the amplifier "sees" ground via the filament.
            BUT WHY do they flicker?

            Pulled headlight switch and cleaned spade connectors. One had minimal oxidation. Still not better. No auto dim or delay btw. Plain switch.

            I also noticed that any time I reconnect the battery ground and turn on the taillights the brake/turn lights fully light up for about 10 seconds, then drop to the slight flicker mode. What´s ging on here? That´s definitely not normal.

            Comment


              #7
              If the brake filament is getting intermittent signal, you may have to adjust the brake switch to be "more off" or replace the brake switch. I'd say check the high mount brake light, but I don't think those were a thing until later. That would let you know if that's coming from the brake switch or the multifunction switch. I don't see how the multifunction switch would back-feed the brake circuit, but it might be possible.

              Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
              rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
              Originally posted by gadget73
              ... and it should all work like magic and unicorns and stuff.
              Originally posted by dmccaig
              Overhead, some poor bastards are flying in airplanes.

              Comment


                #8
                Replace the brake switch. It might look good, but they go bad. A new switch is not expensive, just get a good brand.

                Comment


                  #9
                  Apparently I have one spare from my 84 F250. I´ll try it.
                  But the flicker is only with lights on. Not when they are off.

                  Too bad that the multifunction switch is not easily acessible for spray cleaning.

                  Comment


                    #10
                    If the brake light switch doesn't work... Could one of the brake light filaments be touching the other filaments that come on with the headlights and sporadically back-feed power into the brake light circuit?
                    -Phil

                    sigpic

                    +1982 Ford LTD-S Police Car. Built 351w, Trickflow 11R 190 Heads, Holley Sniper EFI, RPM Intake+ Hyperspark dizzy, WR-AOD, Full exhaust headers to tails. 3.27 Trac-Lok Rear. Aluminum Police Driveshaft. Speedway Springs+Bilstein Shocks, Intermediate Brakes, HPP Steering Box.

                    +2003 Acura CL Type S 6-speed

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                      #11
                      Still flickers with brake switch disconnected.
                      I noticed that the insturment cluster, ATC and ashtray lights also flicker in sync with the brake lights. But not every time.
                      Yesterday I had the flicker on one way. When returning they did not flicker once - cruise worked all the way when the lights were steady of course.

                      Sometimes when starting the car the dash illumination flickers up and then goes out after a few seconds. And that is with lights OFF! Just after starting the car.
                      I believe this is a hint to the whole issue. But don´t know where to hunt for.

                      Comment


                        #12
                        I know it might be a long shot, but make sure the voltage regulator is working correctly.
                        You most likely have an intermittent short somewhere in the power distribution. Or a bad ground, but you've checked those in the engine bay atleast...
                        1985 Mercury Grand Marquis LS, "Maisa"
                        1995 Chevrolet Caprice Classic STW, "Sally"

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                          #13
                          Yah, I was going to ask if any of the flickering occurs with the engine off..
                          1985 LTD Crown Victoria - SOLD
                          1988 Town Car Signature - Current Party Barge

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                            #14
                            Yup, no matter if engine off or on - flickers. But like I said not everytime.
                            Regulator is still from 1984. I definitely gotta check the connector for oxidation and ground at the housing.
                            how would I know it´s defective?

                            Comment


                              #15
                              PO had installed a new alternator. Could it be that my regulator needs terminals jumpered momentarily for a reset? My ´56 Cadillac needs that to be done anytime the generator is disconnected from the harness but I know that generator and alternators are different. So maybe I´m wrong in my guess.

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