Temp gauge pegged - Standard fixed didnt work

[im4darush]

I am working on a 72 C10 with gauges. Temp gauge is always pegged HOT. No matter if key is on or off. I tried grounding the bottom terminal on the gauge and that did nothing. Even ran a new clean wire from the key on - hot terminal to the sending unit and still same - pegged hot. Sending unit is new and no Teflon was used. Motor has a ground strap from the head to batt negative, and then another from batt negative to frame. There are no ground straps to firewall. There is no change at all in the needle position. Can this just be a bad gauge?

[davepl]

Disconnect wire (or lift off signal PCB terminal on the back) from back of gauge. What happens?

If you can't get the gauge to read C, it's the gauge. But likely it'll be fine. You'll find you're shorting to ground somewhere, which will reveal itself when you add stuff back. Start by putting the PCB back on the gauge, but disconnect the harness. Then plug the harness in but make sure the green temp wire isn't connected anywhere. And then connect it to the sender, and finally, let it heat up. Not until then should it swing H, and if it does, you've found the step where it happens.

I forget what all goes on the back of the gauge in terms of ceramic resistor and so on, its been a while, but make sure that's all right of course.