Instrument cluster lighting problem

Discussion in 'Troubleshooting & Diagnosis' started by gensurg73LT, Aug 18, 2017.

  1. gensurg73LT

    gensurg73LT Member

    56
    1
    Jun 13, 2015
    Glen Rose, Texas
    OK I need some help. No lights on the right half of my 72 SS instrument cluster, so can't see the tach, temp, or clock at night. I assume replacement of the circuit board is in order, but then how's the best way to bench test the cluster before replacing in the dash? Do I need an additional wiring harness plug?
     
  2. Twisted_Metal

    Twisted_Metal Moderator Staff Member Lifetime Gold Member

    25,258
    284
    Feb 26, 2004
    Bloomington, MN
    All of the background lights are on the same circuit.

    The problem is most likely a couple of burned out bulbs or corrosion in the bulb sockets.
     
  3. gensurg73LT

    gensurg73LT Member

    56
    1
    Jun 13, 2015
    Glen Rose, Texas
    Last week I had everything out to repair the broken mounting tabs on the gauge housing and while out I carefully inspected the circuit board and all the bulbs. All seemed in good order. I know the dash/gauge lights connect to the gray wire at the connector, but I also don't have my high beam light which should be the light green wire. Anyway, trying to replace the upper bulbs with the wire harness crossing over the speedo cable above which is the crossover AC duct is virtually impossible. So if I'm going to the extreme hassle of pulling the cluster out again, is there a method of bench testing before replacement? Also I guess I'd better carefully examine the factory circuit board connector/contacts. I was really hoping to not have to pull everything apart again.
     
  4. Twisted_Metal

    Twisted_Metal Moderator Staff Member Lifetime Gold Member

    25,258
    284
    Feb 26, 2004
    Bloomington, MN
    Follow the traces for the lights back to the plug.

    I used a 12v trickle charger to test the circuit.

    You can hold a nail with each clamp to use the nails as probes.

    Clean the socket contacts, inside and out.

    Good luck
     
  5. gensurg73LT

    gensurg73LT Member

    56
    1
    Jun 13, 2015
    Glen Rose, Texas
    Thanks. Similar idea I was considering. I guess I'm committed to taking out the instrument cluster again. I may go ahead and replace the circuit board, clean all contacts, polish the harness plug contacts, bench test as you mention, and hope for the best
     
  6. gensurg73LT

    gensurg73LT Member

    56
    1
    Jun 13, 2015
    Glen Rose, Texas
    Thanks Twisted. Trickle charger worked perfectly.
     

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