Fuel gauge-dual tanks

[vitamin_c95]

So I also have an inop fuel gauge. I've searched the forum and found the fuel gauge diagnostics 101 thread and used it to trouble shoot. Basically, when I was trying to install a new lap belt, I accidentally found my tan wire that goes to the gauge tucked away in the cab corner. My gauge is always stuck at the 3 o'clock. When I grounded it, and the gauge goes to empty. So how does this come in to play when i have 2 tanks? I have two saddle tanks, not a behind the seat tank. How do I hook this wire up?

[RustyPile]

I need more information.. Is your tank setup a factory installation or aftermarket?? What type of switching arrangement do you have for switching fuel flow from the tanks?? Do the tanks have fuel sending units installed?? What year is your truck??

[vitamin_c95]

It's a 1971 c20 Longhorn. It's a factory set up. Tank behind the seat is not there, but I do have a filler cap in the cab for it. I have no intention of reinstalling that tank. I assume both tanks have a sending unit, that was my next step to check when I figure out how to route this wire. As for the switching, I have the brass valve on the floor by driver (3 way).

[RustyPile]

For the gauge to work, you'll need sending units in each tank.. The "mechanical" fuel switching valve can be left in place if you wish.. You'll need to install a single pole - double throw, always "on" switch between the gauge and both sending units.. The switch will have 3 terminals.. Locate the switch in a convenient location.. Connect the tan wire from the gauge to the common terminal on the switch.. Connect wires from the sending units, one to each of the other terminals on the switch.. When you select a certain tank with the valve, select that same tank with the gauge switch..

There are other methods that incorporate a single combination valve/switch arrangement, but it entails a much more complicated plumbing and electrical installation.. The method I described is very simple and effective..

[vitamin_c95]

Makes sense. Hopefully I can verify sending units in tank this weekend.

Thank you for your reply

[jbarron]

Easier to get a tank switch solenoid from a square body truck.
Hook it to a switch and the tank switcher will automatically select the right sending unit along with switching tanks.
Way better than the manual valves.