My gas gauge dosen't work. I have a cab setup for dual tanks however my frame has only one tank. I checked the gauge for power and found that if I put my test light on the positive terminal the light will blink. Is it supposed to do this? Is the gauge supposed to have a constant 12v of power?

 

it is powered through the resisitor on the back of the guage pod. the orange wire out, goes to the harness, if you dont have dual tanks, the extra wire just sits there.

 

If your needle isnt moveing and the sending unit has power, pull it and check your float, it may have a small hole in it and therefor full, you can pay about 5 bucks for a new one or if your good with a soldering iron, shake the old float till its empty (or heat it up a lil till its empty...carefully) but id would go for the new one.

 

Is the gauge supposed to have a constant 12v? Mine seems to have intermittened power to the gauge. I took out the sending unit it seems to work ok. Itested it with an ohm meter. The resistance changes as you move the float however I dont know the spec. for it. Can I just run another hot wire to the back of the gauge and use the ground from the tank sending unit?

 

the power runs through a reducer first. the little box thing screwed to the back of the cluster.

 

Since no one else has actually answered your question, here it is.....
NNNNNNNNOOOOOOOOOOOOOOOOOOOO!
The gas, oil, and temperature guage have a common voltage source from a component called the instrument voltage regulator or IVR. It is mounted on the back of the instrument cluster. A small silver can, kind of rectangular and connects to the PCB with 2 contacts similar to a 9 volt battery. It is a mechanical make/break thermal regulator that interrupts current as the internal element heats and cools. Your's seems to be operating properly.

Ford's gas gauge system is higher resistance (75 ohms I think) at lower tank level. As the tank fills up the resistance drops toward zero. If you ground the wire at the tank sender the gauge should peg at full.

If you run 12v straight to the gauge you will ventilate all the magic smoke from it and it will no longer work.

The tank selector switch also switches the gauge to the proper tank sending unit. Try changing position on the switch. You could also check the resistance from the non-power (ground?) side of the guage and see if you have continuity to the sender.

Good luck and let us know what you find.

 

No on constant power .

The Sending units run off of 5v pulsing power.

 

Well I fixed the gauge last night. I think the problem was in the fuel tank selector switch. I checked the gauge, the sending unit and the ground at the tank and everything checked out okay. I cleaned the switch with contact cleaner and put everything back together and now the gauge works! The switch does not work every time you move it though so I need to find a new one. Thanks for all the advice.

 

If you only have a single tank why not bypass the switch all together?

Glenn