JD 3720 fuel gage inconsistent with idiot light

Catenary Kid · May 9, 2024

Troops,

Took the sort-of-new-to-me tractor for a spin around the back 11 yesterday which is all standing on edge, some of it pretty seriously. About halfway through my traipse, the low fuel idiot light came on and the fuel gage started acting posessed, reading from 3/4 to 1/4 with stops in between. The idiot light stayed on consistently. I took the tractor back to the barn which is fairly level, idiot light on - gage at 1/2. Where do I start looking?

Runner · May 9, 2024

Sorry, I am clueless on fixing stuff like this. However, I am curious, do you have any idea how much fuel is actually in the tank? Was any of the readings anywhere close? I don't put much faith in Deere fuel gages.

My 2007 JD 2520 will run for at least two hours when the gage is firmly on the E mark. Has been this way since new. Guess this is better than having it stop dead as soon as it gets close to E.

loggin · May 10, 2024

Catenary Kid said:
Troops,

Took the sort-of-new-to-me tractor for a spin around the back 11 yesterday which is all standing on edge, some of it pretty seriously. About halfway through my traipse, the low fuel idiot light came on and the fuel gage started acting posessed, reading from 3/4 to 1/4 with stops in between. The idiot light stayed on consistently. I took the tractor back to the barn which is fairly level, idiot light on - gage at 1/2. Where do I start looking?

First and cheapest thing to look at would be wiring to make sure there is no damage and then have a look at the sending unit in the tank. You can remove it and test it with a multi tester. If it is not those than it might be the instrument cluster which will require it to be removed and taken to someone knowledgeable in fixing electronics.

Hope this helps!

Catenary Kid · May 11, 2024

Many thanks, all, for the suggestions and advice. I dipsticked the fuel tank to find that it was about 1/4 full, not low enough to trigger the idiot light, I'd suppose, but still. So I checked the wiring as far as I could, then when I started it to take it out to fill it up, found the low fuel light was out and the gage read correctly. Once the tank was full, everything worked as it should, so I'm assuming either something in the wiring that 'righted itself' as I was fiddling with it, or just an anomaly due to the incredibly rough terrain. Nevertheless, all's well at the moment....again, thanks!

Tinhack · May 11, 2024

Wiring will never fix itself. Your description would lead me to believe there's a loose/corroded connection or a chaffed/chewed and shorted wire somewhere. Look for evidence of rodent damage at all pockets and flat areas.