Low Fuel Indicator

I know the low fuel light topic has been around forever. I have a 69 XR7 with the low fuel option. I have the 3 prong sending unit. The low fuel relay behind the dash was missing so I got a used one from WCCC today. I plugged it in and the low fuel light on the instrument cluster came on and stays on, even without a key in the ignition. I don’t think that’s right. Any suggestions on why the light stays on?

The prove out wire may be on the wrong side of the starter solenoid?

Which one is the prove out wire?

At the starter relay it’s the small red wire with the yellow plastic molded connector on the starter cable terminal.

Are you referring to this wire? It needs to go to the other pole on the relay?

Maybe. Try taking it off that post. Is ‘69 different from ‘68? Maybe Scott knows?

The indicator light should only come on when the key is in the start position and go out after the engine starts. It would also come on when the thermistor assembly on the fuel sender is exposed to air. (Less than about 4 1/2 gallons of fuel in the tank). Is the wiring to the starter solenoid original? Can’t tell from your picture.

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The wire harness in the engine bay is original but there has been some repairs done before. Looks like all the wires close to the relay have been cut, spliced and heat shrinked. Wires look to be the same colors and guage. If the prove out wire is the one in my earlier picture, it is solid red and on the positive side of the relay. Should it be on the negative side? I don’t want to just move it over there yet and fry something. I removed the plastic wire loom for hopefully better pictures

That wire is the low fuel prove out. Should be on the starter side. If you’re nervous, just disconnect it and see if light goes off.

Correct, that wire goes on the other side.

Changed that wire from positive side to negative side. Low fuel light went out, no sparks! The low fuel light does not come on for a few seconds when in accessory or run, but does come on with key in start position. And light goes back out once started and key goes back to the run position. Is that correct?

That is how it should work.

Thank you all for the help, you all are awesome! So now I have a good excuse to drive the car around in the nice weather we have been having to let the fuel get down low enough to see if the light comes on when it should. Maybe I will carry a little gas with me just in case! Lol!

Unless it’s been rebuilt by me it is highly unlikely that it works. So far I have never had a sender come in with a working thermistor. The good news is that over time fuel senders read lower and lower, showing you an empty tank earlier than reality. They also never go to full.

And I am pretty certain mine falls into that category. It reads less when full and empty when I know there is fuel in the tank.

When you get around to it, send it to me. I can make it more accurate than even most of the originals, and the low fuel light will work again. It runs $125 including the return shipping a new brass float, seal ring, filter, thermistor and return postage via Priority mail. Takes less than a week.

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