So here's a long term thought for me...

Truck has the factory tank at the rear, which connects up to the normal fuel gauge in the lower left of the cluster. My f-i-l added an auxiliary tank in front of passenger rear wheel



with a selector switch down between the driver's seat and the door.

He also added separate oil pressure, voltmeter, vacuum and altitude gauges on top of the dash.

The only gauges working currently in the cluster are speedo and fuel, and with the extra gauges fitted, the oil pressure and ammeter gauges are not so important.

So, has anyone replaced the voltmeter with another fuel gauge, and then wired it up to a sender for an auxiliary tank? That way, the estimated contents of both tanks could be shown at once, if the auxiliary tank has a sender or can take one, of course. I realize that the PCB wouldn't work for this, so would need "adjusting".

 

Yes the PCB could take it. Think of the Fuel, Oil, and Temp gauges as the same piece - but different print on their faces. The senders all look different, but I'm pretty sure they all send similar voltages or whatever.

I think you could swap your fuel and temp gauges and they'd still work. So I'm thinking that if you put another fuel gauge in place of the original oil or temp gauges, and then extend their sender connector wire to the tank, it should work, as long as the other tank's sender is the same as what these trucks came with.

Good idea!

 

assuming there is a sender on the auxiliary tank, and that the sender works the same way as the factory tank (similar resistance) one could wire in a "two in-one out" switch, and use the one gauge for both tanks.

 

I think that's the better solution.
First of all, why lose a perfectly good volt-meter? Do you have other electrical system monitoring gauges?
Second is why mess with a working PCB on one of these things too? Not only are they delicate and finicky sometimes (though if you can work on that type of stuff, then that's probably not an issue), but it sounds like a TON more work than needed.
Even the factory installed 2 tanks in these things. All they did was use an electrical switch on the dash like was mentioned. You can do the same and away you go.

Much quicker and easier I would think.

Paul

 

There is no voltmeter in the instrument cluster, just oil pressure, ammeter, fuel gauge and water temperature, plus the speedometer.

I already have a functioning voltmeter and oil pressure gauge sat on top of the dash that my father-in-law fitted - the OP gauge presumably because either the cluster one stopped working, or he wanted actual pressure figures rather than Low, High, or somewhere in between.

The idea of retro-fitting the fuel gauge switch heater control set-up might work, too.

 

Sorry. Misunderstood your previous statement (reprinted below without permission) and thought your plan was to modify the existing cluster to suit your need of a second fuel gauge.
Didn't analyze it too much, because maybe you'd already placed a volt meter in place of the ammeter, like many here do. Or maybe you use the term "volt-meter" when talking about ammeters, as many do too.
You did mention volt-meter, another fuel gauge and PCB in the same paragraph. With those previous thoughts in my head, it made me think you were planning to take the cluster apart.
So I used a little too much poetic license I guess, and moved a few steps in my head, but in the wrong direction.

The swap for the factory dual-tank control would be the slick way to do it for sure. My PO just put a switch in the dash. Wanted to do it the factory way myself, but frankly it never gave me any trouble and doing the extra work just didn't sound fun at the time.
After all, I often live the "It's only temporary. Unless it works!" lifestyle.

Paul