Optional 3 pointer gauge problem

Discussion in 'Sparky's corner' started by MNBelv57, Aug 6, 2019.

  1. MNBelv57

    MNBelv57 Well-Known Member

    Hello all. Hope everyone is having a good summer. I was wondering if I could get some advice on diagnosing a problem I am having with an optional gran sport style (3 pointer, gas,oil, temp.) gauge I recently installed to replace the stock idiot light gauge. The GS style gauge is from a parts car and It did work when I had it on my other Regal. The car I have it in now is a 1975 Regal. The car it came from was the same year and model but had this option. The problem I'm having is that when I turn the key to start the engine, The temp. and oil pointers peg down to the lowest level and stay there till I shut the engine off. The fuel pointer is unaffected as I assume that is on a different circuit. This also happens when I turn on the headlights with the engine off, I checked my service manual and one of the causes listed was a bad ignition switch. But since it is doing it with the ignition in the off position I'm starting to think maybe there is a ground in the lighting circuit, If anyone has any advice that can make tracking down this problem easier I'd appreciate it. Also, how can I check the gauge to see if it is working properly ? I have a multimeter, so would I do an ohms check or a voltage check with power to the gauge and how ?
    Thanks, Mario
  2. 1973gs

    1973gs Well-Known Member

    Do you still have the car that you removed the gauges from? If it's the same as my 73 GS, there was an adapter harness that went between the factory harness and the gauge cluster that the idiot light cluster didn't use. Without that harness, you'll probably have to move some wires around in the harness. The factory service manual should help if you need to play musical terminals.
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

  4. MNBelv57

    MNBelv57 Well-Known Member

    Gentlemen, thank you so much for your insight on this problem. I don't think I would have ever figured it out that there was a separate harness adapter since the other car I had it in had some electrical work done to it to adapt electric doors in place of the original manual ones. So, most likely the optional gauge was worked on too because I don't remember taking an adapter off the previous parts car. I will follow the instructions you posted and let you know how it comes out. By the way, I agree about having the back up mechanical gauges. I have the three pack (amps, temp., oil) under the dash.
    Thanks again, Mario.

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