Removed my instrument cluster today

Discussion in 'General Ranchero Help' started by john777, Apr 16, 2019.

  1. john777

    john777 In Fourth Gear

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    496
    Also, did only GTs have tachs? And if so does anyone have a wiring diagram that has a tach on it?
    My 72 wiring diagram has no tach on it
     
  2. john777

    john777 In Fourth Gear

    Messages:
    496
    And if there is anyone out there who considers themselves an expert on a 72 year type electrical issues, please mPM me your phone number if you can take a call. I have no power going to the tach via the red blue dot wire.
     
  3. colnago

    colnago In Fourth Gear

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    488
    Location:
    Ridgecrest, CA
    I thought you could run a wire directly from the coil to the tach. That's how I'm using an aftermarket electric tach in my '67 F250.

    Joseph
     
  4. andrewok1

    andrewok1 In Maximum Overdrive SILVER MEMBER GOLD MEMBER

    Messages:
    3,389
    Location:
    ocala ,florida
    tach only with ralley gauges , mostly GT


    This is the factory harness that connects the harness on the back of the cluster to the engine wiring harness:

    [​IMG]

    This is the factory engine to fuse block harness that contains the integral tachometer and ammeter wiring:

    [​IMG]

    For those that are troubleshooting Tachometer or ammeter wiring issues or those retrofitting a gauge cluster into a standard car the following rough sketches show the proper wiring paths:

    1972 through 1976 (Green Printed Circuit) Tachometer:

    [​IMG]

    Ammeter: To properly install the wiring for the ammeter you need an insulator junction block, one or two (recommended) 14 Gauge fusible links, 30-36 inches of yellow 10 gauge primary wire, and yellow and red 14 gauge primary wire (approximately 12' of each). Install the insulated junction block on the flat boss under the starter solenoid, take the original primary wiring off of the starter solenoid and attach to the insulated junction block, then install the shunt per the diagram below:

    [​IMG]
     
  5. john777

    john777 In Fourth Gear

    Messages:
    496
    Thanks for all the help. Nothing worked. I’m going to get an aftermarket tach with a shift lite anyway. Can’t read the factory tach going down the track. The right blinker light is not working as well. Hopefully this will be the LAST time I have to put the cluster back in.

    Does anyone have a clue why the right blinker is not part of the printed circuit board?
     
  6. NeillNZ

    NeillNZ In Second Gear

    Messages:
    32
    Location:
    New Zealand
    I'm not sure anyone will know for sure why. As someone who has studied these printed circuits a lot(maybe too much) I think it might be a simple as they could not fit the traces onto the design. There is no space left to get the required traces to the lamp connections, bear in mind there would need to be two, a ground and the lamp power. Maybe the guy who did the layout back in the day was in a hurry :)

    [​IMG]
     
  7. 72GTVA

    72GTVA Administrator Staff Member

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    Location:
    Chesapeake, VA
    [​IMG]

    Looking at the plugs above, the red two pin dongle hanging from the printed circuit connector is the RH Turn Signal wiring (ground and lamp power) which suggests that NeillNZ is correct - the printed circuit designer likely didn't have the time to work out the pathway in time for production for '72/'73.
     
  8. john777

    john777 In Fourth Gear

    Messages:
    496
    Thanks guys. My buddy is going to come help me out and re-install everything this am. Will place after market TACH in but still not sure why the right blinker lite won't work....But your explanation makes perfect sense
     

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