Amp gauge not working

Discussion in 'Electrical Systems' started by fvdillon, Sep 29, 2018.

  1. fvdillon

    fvdillon Veteran Member Lifetime Gold Member

    Messages:
    919
    Likes Received:
    1
    Joined:
    Jul 16, 2000
    Location:
    Crete,IL
    On my 1972 Z, the amp gauge has quit working. Needle straight down, 6 o'clock position. I checked it's not unplugged. Any way to tell if I need a new gauge, or it's something else? I did a search, couldn't find anything. Thanks Jim
     
  2. fvdillon

    fvdillon Veteran Member Lifetime Gold Member

    Messages:
    919
    Likes Received:
    1
    Joined:
    Jul 16, 2000
    Location:
    Crete,IL
    anyone??
     
  3. Jim Streib

    Jim Streib https://www.flickr.com/photos/[email protected]/albums

    Messages:
    448
    Likes Received:
    84
    Joined:
    Apr 6, 2004
    Location:
    Saint Louis, MO USA
    Taking a stab here but your gauge should be one that is NOT a full flow style and connects into the wiring harness at two points and the wires between these two points act as a shunt.

    I also think where these two connections for the gauge into the harness are protected with possibly a fusible link and maybe one or both have blown or the connections into the loom have gone south.

    I also think that both of these wires pass through the bulkhead connector and referencing a wiring diagram may reveal what spot those wires are at in the bulkhead connector to test for power there but I wold think the gauge would have to be out of the circuit or you may get a false positive reading on a meter.

    I did see someone does convert the original style AMP gauge to a volt gauge and I don't know how one would tell and maybe yours got changed at some point ?.

    To do some troubleshooting, you would have to take the gauge out of the circuit and then check to see if both wires to it show battery voltage.

    I also wonder too if the amp gauge has a shunt across the back of it like on some fuelgauges and maybe this if it is to be there has an issue.

    Jim
     
  4. fvdillon

    fvdillon Veteran Member Lifetime Gold Member

    Messages:
    919
    Likes Received:
    1
    Joined:
    Jul 16, 2000
    Location:
    Crete,IL
    Thanks Jim, I'll see if the wires show some voltage. It's original so has not been changed. What the heck I can't get more than 46 years out a gauge? lol Jim
     
  5. Jim Streib

    Jim Streib https://www.flickr.com/photos/[email protected]/albums

    Messages:
    448
    Likes Received:
    84
    Joined:
    Apr 6, 2004
    Location:
    Saint Louis, MO USA
    If you do have the gauge that is wired across two points in the wiring and the wiring is being used as a shunt, then with the gauge in place, both terminals can show voltage with a bad gauge or if one or both leads to it are broken or not connected to power. This is why you have to disconnect the wires at the gauge and make sure each each has power with a meter.

    I'm just trying to explain this so you don't get to the back of the gauge, leave it connected and then reply back that both terminals do show power with a meter. They can but it won't tell you which way to correct the issue as to whether it is a gauge or power delivery to the gauge issue.

    Just be careful and disconnect the battery to get at the gauge and disconnect it and then make sure the wires cannot hit anything or become grounded out. THEN power up the car and test the wires. Once that is done, disconnect the battery and put things back together and reconnect the battery once again.

    Jim
     

Share This Page