The Stovebolt Site Forums The Shop Area The Electrical Bay Where to connect a ground wire to sending unit?

The gas gauge in my 1969 C-10 doesn't work, but reads 1/8 full regardless. I figured it could be any number of things until I realized there is no ground wire on the sending unit.

Where the heck is that supposed to be? Jumpering from ground to both the unit and the locking ring gives no results.

So I've read related posts here in the forums. Do I understand correctly that current is supplied from the gauge to the unit? Is that supposed to be a full 12V?

I've also just tried some troubleshooting. With the meter wire disconnected from the unit, that meter wire has only 8V on it with the key on, and nothing with the key off.

Here is an album of gauge and sending unit pics.
* The 1st is of the gauge with the meter wire connected.
* The 2nd is of the gauge with the meter wire disconnected.
* The 3rd is of the sending unit with nothing connected.
* The 4th is of the unit with the meter wire connected to the input pin.

Any ideas?

the sender supplies the ground to the gauge thru it's variable resistance - power is supplied from the ignition switch to the gauge, not from the gauge to the sender .... the sender should be grounded by it's mounting to the tank - you can check the sender by removing it from the tank and manually working the float arm while you check the resistance from it's terminal to it's case, should vary from 0 to 30 [or maybe by 69 they're 90 ohm?] - you could also check before you remove it, from the terminal to the tank .... I'd suspect your gauge if it shows a constant reading, but it could be the sender

Bill

Thanks very much, Bill...that makes much more sense!

Bill, I just checked the resistance between the teminal and tank with the sender installed. It showed about 12.7 Ω with about 7 gallons in the tank. If the ohm reading is anywhere near linear in relation to the tank capacity, that sounds relatively reasonable. I'm gonna pull the sender and try that again later. Thanks!