Fuel Gauge problem

durwood71 · Jan 17, 2011

I have a 71 Bronco with dual tanks. The Aux tank reads correct on the gauge, but the Main tank reads over full. We have tested the wires; ground and leads to both tanks are good. The sending unit is new and we have tested both post on the sending unit, that is good. The Oil, Temp and Alt gauges all work. What else could it possibly be? ?:?

Viperwolf1 · Jan 17, 2011

How did you test the sending unit? How many ohms did you see?

durwood71 · Jan 17, 2011

Main tank had 43ohms on approx 1/2 tank, Also ran test wires from the sending unit to the switch and ground. The Aux tank which is reading correctly read 11 ohms on a full tank.

Viperwolf1 · Jan 17, 2011

Sender looks ok. I'd expect to see a short to ground somewhere on the orange wire causing it to max the gauge. Other causes could be a miss-wired switch, bad switch, or a bad gauge itself. You can test the gauge by unhooking the orange fuel wire and attaching one of the other sender (oil or temp) wires. If the gauge still maxes then it's bad.

durwood71 · Jan 17, 2011

I can rule out the shorted wire as I ran a test wire from sender to switch and got same result.
The gauge works when switched to the aux tank. The switch is new, I also have the original switch and get same result from both. What you said about miswired makes sense as it only had 1 wire hooked up when I got the Bronco. I thought I had it right but maybe I don't. How should it be wired? Why does it have 6 connections for only 3 wires?

Viperwolf1 · Jan 17, 2011

durwood71 said:
How should it be wired? Why does it have 6 connections for only 3 wires?

It was probably an off the shelf part that Ford used on something else previously.

ol gray mare · Jan 17, 2011

durwood71 said:
Why does it have 6 connections for only 3 wires?

Like he said, off the shelf, but it makes it easy to wire up an electric valve to switch tanks.

73azbronco · Jan 17, 2011

sweet, that saves me a switch!

Fuel Gauge problem

durwood71

Jr. Member

Viperwolf1

electron whisperer

durwood71

Jr. Member

Viperwolf1

electron whisperer

durwood71

Jr. Member

Viperwolf1

electron whisperer

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ol gray mare

Sr. Member

73azbronco

Bronco Guru

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