After suffering through some intermittent gauge problems I decided to replace my circuit board behind the center gauge cluster (1981). One of the problems I was having is that the voltmeter would cut in/out. I tested the gauge per the Willcox method and it tests fine... I even bounced it around a bit to see if I could cause it to fail and it held steady. I reloaded the gauge to the cluster and plugged in the wiring harness and tested at the gauge terminals. Here's what I found:

If I used a direct line from the ground post on the battery directly to the gauge ground terminal and used the wiring harness and replacement circuit board, the voltmeter works perfectly. If I disconnect the direct line to the battery negative and rely on the harness ground, it fails. That prompted me to trace the ground circuit on the circuit board to see which contact on the plug provided the ground..... and that's where I got confused. While there is a ground wire into the harness and parts of the circuit board, I don't see where it contacts this portion of the ground circuit. Is the ground supposed to come from the gauge housing to the mount bezel? I guess my question is... what am I missing here, where does this part of the board pick up its ground?? Look at the pics...

The voltmeter is the bottom left of the circuit board. You'll see 2 terminals just to the right of the light socket at the far lower left corner. The terminal at the 9 O'Clock position is the ground. The terminal at the 6 O'Clock position is +12V (or whatever Voltage value the battery has.) If you follow the circuit from the Ground terminal you'll see it never connects to the plug socket at the center of the board. So where does that portion of the circuit board pickup it's ground?



I borrowed the pic from the folks at Willcox... I guess I could just run a ground wire to the terminal but I have a feeling I'm missing something simple and I'd like to keep things as close to original as I can.

Any help is greatly appreciated.

Thx,

kp

 

The volt meter terminal is grounded to the gauge panel with a nut under the flexible circuit, that grounds the circuit in the flex board for the lower lamps. The fuel gauge is grounded in the same way to send ground to the gauge panel.

 

Thanks for this ... I was thinking about this after I'd left the shop and figured the ground had to be through the bezel mount... I have the washers/nuts on the top of the circuit board at present. I assume that the washer goes underneath the circuit sheet with the nut over the circuit sheet? Will get a chance to change things around this evening, again, thanks for the help!

kp