JD F1145 Fuel Gauge (always shows both tanks full)

ckesey · Oct 21, 2020

I'm about to tear into my f1145 fuel gauge, switch and wirring harnesses. Anyone have any past experience with the fuel level/gauge on these machines? When the key is off the needle goes to empty (which I'm guessing is normal) but when the key is switched on it goes to past full and flipping the tank selector doesn't move the needle. Both tanks should be showing approx 1/2 full at this point.

Having a hard time finding an electrical diagram so if anyone has a picture of this layout....it would be much appreciated.

Thanks for any advise.

joecdeere · Oct 21, 2020

I have a PDF of the technical manual for your 1145, has all the wiring and troubleshooting,
shoot me your email if wanted

Joe

CoyPatton · Oct 21, 2020

Just an off the collar guess, but sounds like a wire shorting somewhere. It could be to ground or to 12 volts depending in how it is wired.
Going to empty or below even is pretty standard for an electrical gauge. Sending units working by changing the resistance in the circuit thus allowing more or less circuit (may be amps or voltage) to flow.
The short could be most anywhere, in the sending unit (less likely since you have 2 tanks and 2 sending units, but again depending on how wired 1 sending unit could cause the issue) itself or in the gauge or in my opinion most likely somewhere in the harness.

ckesey · Oct 21, 2020

Joecdeere...got the PDF and it will be very helpful in knowing what to test where. Thanks for this.

WranglerX · Oct 22, 2020

Typically when gauge goes to full no matter how much or little fuel is in tank, it mean the gauge has a open circuit between gauge and sender, it can also be sender is bad or lost its ground.... I would start trouble shooting at tank sender...

This video will explain a lot on how fuel gauges work.... Note at about 2:25 the ground wire comes off sender and what fuel gauge does...

How To Test a Fuel Sending Unit & Gauge | Old School Way - YouTube

Dale