fuel gauge

[85blueox]

I have an 85 F350 diesel with duel tanks.  Fuel switch is on the heater/aircont. box/consule.  both gauges show 0 even when I add fuel, been that way since I aquired it a year and a half ago.  

If you experts had to guess, where do you think the problem is?  Just looking for a starting point. Since it shows 0 fuel on both tanks I thought maybe the switch, wires, possible the gauge is the problem.  Knowing the wires are always a mess on things thanks to 30 years of crazyness I though it might be the problem.  

[Gary Lewis]

We have a page at Documentation/Electrical/Gauges that might help.  On the Troubleshooting tab is the suggestion to pull the wire off the sending unit and ground it - with the switch pointing to the tank of course.  Turn the key on and the gauge should go to Full.

On the Gauge Circuits & Spec's tab there's a schematic of the wiring and you can click it to make it bigger.  But to easily see it go to Documentation/Electrical/EVTM/1985 EVTM and then scroll down to Fuel Tank Selector & Gauges (Diesel).  There you'll see that the Y/W wire goes from the switch to the gauge, so if you were to ground it the gauge should peg as well.

[viven44]

For the diesel (same as 460), I believe the Y/W wire goes from the on-frame selector valve harness to the gauge. (Pin 4 on the harness.) Grounding pin 4 Y/W on that harness should make the gauge go full, if it doesn't then I think its likely the gauge or connection to the gauge on the printed circuit board.