Have some Lights, but not others, Help!

Electrical and Ignition

  1. Snake Oiler

    Snake Oiler Member

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    1973 Plymouth Duster with 360. I have headlights, parking lights, all 4 side marker lights, horn, reverse lights, break lights and dome light. I dont have tail lights, dash lights, turn signals, fuel gauge not working, temp gauge not working.

    I have replaced bulbs, socket PC Board and bypassed the amp meter. I replaced the step down capacitor , Fuses are good. So maybe it's the ground? Where though? Headlight switch seems fine. Standing by for the brilliance on this forum. Thanks - Snake Oiler
     
  2. Snake Oiler

    Snake Oiler Member

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    BTW we have established ground on the back of the cluster housing (metal). I have a very talented Jack of all trades friend with me testing for ohms and all sorts of things with his meter.
     
  3. TrailBeast

    TrailBeast Slightly Twisted Member

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    Well, that was the first thing I was going to suggest.:D
    There are wire diagrams for a lot of the cars over at MyMopar - Mopar Forums & Information - Mopar Wiring Diagrams
    Then all you have to do is trace it down.
     
  4. Snake Oiler

    Snake Oiler Member

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    Thanks, yes we have that diagram. Looks like my expert is pulling the cluster out. He thinks it might be the light switch, although the connector for that and its operation seemed fine to me. Thanks for response.
     
  5. Snake Oiler

    Snake Oiler Member

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  6. Snake Oiler

    Snake Oiler Member

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    Ok, we took out cluster, found that the metal backing has a constant 8v and the lights came on and the fuel gauge worked with the key on. As soon as we put cluster back in car, the 8v grounds out and lights go out. Is this normal as we might be missing some insulation as it attached to car? Also I think the reason its 8v and not 12v is because of the step down capacitor. We thought we had a wire switched in the connector, but there is only one lead that has voltage and the rest are ground. So polarity reversed? So it might be as backwards, but all light work now with cluster hooked up and out of car. Wow.
     
  7. 67Dart273

    67Dart273 Well-Known Member

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    "step down ??" Are you talking about the instrument voltage limite? That only feeds the gauges. But PC boards can develop problems AND THE ONLY GROUND for the cluster is when mounted, through the screws. Good idea to provide a separate ground pigtail for the cluster

    Here's an old repair thread on clusters:

    Printed circuit pins repair

    Also, please don't depend too heavily on the aftermarket diagrams at MyMopar. They leave out many details/ options/ connectors. There's a 73 shop manual there, and it and some others by the way, came from the guys right here
     
  8. 67Dart273

    67Dart273 Well-Known Member

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    Exactly where are you measuring this 8V?
     
  9. Snake Oiler

    Snake Oiler Member

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    We are measuring 8v on the whole silver metal back of the cluster. So when it is installed back in the car with screws, it grounds out and the lights go out. Otherwise every single light works on the car now.
     
  10. 67Dart273

    67Dart273 Well-Known Member

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    OK with the cluster out, there is no ground to the cluster, so of course it will measure "some voltage." The cluster must be grounded to properly operate. If you are getting some lights with the cluster "out" that is a wrong road you are traveling. You've created a feedback/ loop/ etc

    The gauges, except ammeter, are powered from a sort of regulator, variously referred to as an IVR, instrument voltage limiter, instrument regulator, etc. It's a small rectangular box, plugs into the rear of the cluster. If you read the thread I posted, it mentions fixing the board where that fits. The harness connector on the board is troublesom

    The dash lights are a "trick." There are TWO power supplies to the headlight switch. One large feed, NOT FUSED comes off the ammeter circuit, and there's a breaker on/ in the light switch. This feed powers ONLY the headlights

    The tail /park circuit is fed off a fuse which is hot at all times, so you need to see if you are even getting that power to the light switch.

    The dash dimmer control (twist the knob) ALSO gets power off the above tail / park circuit. The output from the dimmer then feeds TO the fuse panel "inst" fuse-----on one end of the fuse panel.......so that fuse won't show power unless.........

    The tail circuit is getting power from the fuse supplying it..........the light switch is in park or head..........and the dimmer control is twisted "some" left

    Then that dimmer controlled power goes through the inst fuse and supplies all the dash lights through ORANGE wiring. If you see an orange wire under the dash.......radio.....ash tray.......heater controls......cluster.......that is dash dimmer controlled power
     
    Last edited: Apr 12, 2019
  11. Snake Oiler

    Snake Oiler Member

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    Ok, thanks we will try a few measurements for power in the right places that you suggested. The link describes the pin fix in the barrel connector. My connection there us sturdy and strong, no loose pins.

    I get the IVR. I have had several A bodies, but none has developed this feedback/loop. What is interesting is that if you follow the PC pattern from the IVR, it looks as if the lower voltage feed goes to other places on the board, and voltage even travels to the screws holding down the PC to the housing with smaller screws.

    I think we have a reverse polarity issue. Another thing I noticed is that the LED bulbs I put in the new sockets have a polarity functionality. You need to set the bulb in the socket a certain way or the light wont work. I never knew that to be the case. We just need to find out why we have higher that normal voltage on the back casing and why when it hits ground on the car, the lights go out instead of completing a circuit. Thanks for your help
     
  12. Snake Oiler

    Snake Oiler Member

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    Any suggestions why I have a reverse polarity issue? See explanation above. Just trying to refresh thread. Thanks
     
  13. 67Dart273

    67Dart273 Well-Known Member

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    You cannot reverse polarity anything.......except LEDs is that what you have?.......without connecting the battery backwards, and you DON'T want to do that

    some LED bulbs can fit into the socket either way, and the twist in cluster sockets can also fit either way. I think the dome light is another one It won't damage the LED bulb, they simply won't light
     
  14. Snake Oiler

    Snake Oiler Member

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    Yes I did find out some of the LED lights you can reverse polarity. The issue I have is every light on the car now works if the cluster is not attached to the car. As soon as I put it in the - and attach the 3 screws and it grounds all of the - lights go off. I am getting 8 V on the back metal housing of the cluster and I am figuring it is grounding outAnd making the circuit in complete when I put it in the car. It is baffling to me.
     
  15. 67Dart273

    67Dart273 Well-Known Member

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    Without being there, hard to guess. But you are allowing a "non standard" situation screw with you. In other words the cluster MUST be grounded, so you have created a "false" situation which (for whatever reason) caused the lamps to light. You are leading yourself down a wrong path. Ground the thing, check voltage to the affected lamps, and if that is OK, then deal with the lamps. "I bet" the lamps are reversed. If you can't do anything else, dig out (or buy) a couple of incandescant lamps to troubleshoot with, then see where you are with the LEDs
     
  16. Snake Oiler

    Snake Oiler Member

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    Ok I will try to chase with those bulbs. Thanks.
     
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