Fuel sending unit wire

If the temp gauge isn't working, you still may have a problem getting power to the gauges. Here's the general flow

The instrument limiter gets 12V in run from the key, drops down the voltage, and splits it off to any instruments, gas, temp, oil.

You should be able to GROUND the sender end of either the gas or temp gauge with the key in "run" they should peg.

There is no power "from" the sender. The sender end of the gauge goes directly to the trunk through one wire, to the sender, through the sender to ground.

So you should be able to check continuity of the wire / sender with a meter. IF you doubt the sender is working, pull the wire off the gauge and tank, and ground one end with a clip. Then you can use your meter/ light and a battery to check continuity.

MAKE SURE the sender is grounded. There normally is a clip that jumpers across from the metal line on the sender, across the rubber connector hose, and clips onto the metal fuel tube heading up front. It doesn't matter if you have that exact clip, so long as the sender is grounded.

One way to check "end to end" and remove the sender from the equation is clip a ground to the sender end of the wire. If the gauge is working, it should peg full with key in run.