Ok, on my 70 F250 My fuel gauge does not work at all. I have the aux side tank which doesnt work either. I have tried 2 different fuel gauges, a new printed circuit. a different voltage regulator. Took out the float/sending unit in the cab tank. The float was good. I cleaned the connections and ground. I also tried taking off the orange wire and grounding that. Still no change. Stays on empty for both tanks. Could both sending units be bad?

 

Do you have toggle that switch for just switching to the other tank? or do you have the electric one?

Or the manual fuel switch under the seat?

My brother had a C/S XLT Ranger with all electric tank switch ford had was cheap and did not last very long. It should be lower left side of dash.

Look under cab where were the two fuel lines connect the a wired switch. Most part houses can get them.
Orich

 

Ground the sending unit wire at the tank. If the gauge goes to full then the circuit from the tank to the dash is good and the problem is in the tank (probably the sending unit). If the gauge doesn't move start following the circuit back to the dash.

 

ALL 1967/72 F100/350's with in-cab tank and optional factory installed auxiliary tank have a manual control selector valve on the floor next to the drivers side of the seat.

The toggle switch on the far left side of the dash...only changes the dash fuel gauge from one tank to the other.

Ditto 1973/74 F100/350's with dual fuel tanks, except the switch is located in the heater control panel.

1975/79 F100/350's with dual fuel tanks have an electric fuel tank selector valve and solenoid assy mounted on the frame rail.

The switch located in the heater control panel changes the tanks and the dash fuel gauge from one tank to the other.

 

I have the toggle switch for the tank gauge and then the valve lever on the floor to change the fuel source. I took apart the aux fuel gauge switch and cleaned it, put it back together. Still nothing. I also took the orange wire off the sending unit and grounded it. Still nothing. It also appears that none of the other gauges work either. no temp no oil pressure no voltage.

 

Take the float out again. Open up the square sending unit. Gently pry the tabs up and carefully take the cover off. Look to see if the copper windings and copper contact is clean and making contact. Mine was gummed up and wouldn't read completely full. Once it is clean, test it while you have it out. make very small adjustments on the float contact.

 

I think I got it! I decided to reseat and clean the connectors along the way. I think it ended up being the gauge cluster connector of all things. It looked good to me at first but obviously it wasn't clean enough. Just took a bit of sandpaper and made the connectors look shiny, plugged it and everything works. Thanks for all the help. It was a learning experience.

 

Simple stuff ~~~Age related brain teasers,
Orich

 

Yup. The simplest solution is usually the best.

 

What works better and doesn't remove as much metal is the old abrasive pencil erasers. The red ones on the end of Ticonderoga pencils.
One just erases the corrosion.

 

Ha~~good for everything!
Back in my 2th or 3rd grade class, I saw a kid in the boys restroom using a erases on his front teeth..
Orich