CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Fuel gauge issue

I bought my 59 f100 last year as project truck that had electrical gremlins and needed brake lines. I just finally got around to geting the whole brake line done as I’m no macanic so I dident jump right into it. But now I’m on the body work and electrical. Here is where my problem lies most of the original harness has Been cut and spliced with the wrong color wires and ect. I went to hook up my fuel gauge to the sending unit as shown from my wiring diagram and it started smoking . So I unhooked it quickly and haven’t messed with it since . Could this be the voltage regulater on the back of the cluster or the wrong sending unit for my truck ? I don’t want to have a bomb on my hands . the gauge is a the orig i think it is a 0-30 ohm . I do not know about the sending unit .also how would i be able to tell if the voltage regulater is bad? any help will be appreciated.thanks.http://i1132.photobucket.com/albums/m579/1959f100/1f995257.jpg

You’ll want to get connected to vintage F100 folks, I would think there are forums for them. You might also get a copy of Hemmings Motor News, there’s probably somebody who sells a replacement wire harness for your '59.

If you plan on rewiring the truck yourself, at the least you’ll need a schematic from these guys for $18.00.

http://www.classiccarwiring.com/fordtruck.php

Tester

Tester i do have that.i wired the sending unit to the way that schematic shows. After i hooked up the sending unit up the gauge started to smoke.

If the gauge started to smoke it’s not a voltage issue. It’s a amperage issue. It could be the gauge is so old that the slight amount amount of amperage it saw burned up the windings for the electromagnet that makes up the gauge.

Tester

So should I try aftermarket?

You have no choice. Unleess you can find an original fuel gauge for a 59 F100.

Tester

Not sure if this helps you but here’s a schematic I got when I was close to getting an F100.
(Ended up getting a 52 dodge truck instead.)

Looking at that schematic a bit more, I bet that gauge regulator is busted. They used to use a bi-metal switch that would turn on and off depending on the load - kinda like a turn blinker. It is a clever way to drop voltage without having to dissipate the heat normally generated by whatever voltage you’re dropping, an old school way of regulating.
Anyway, I bet that thing is shorted, putting the full battery voltage onto the gauge and tank level sender. That is probably where the smoke came from.
Those things may very well still be available, but should they not be, you may be able to replace it with a simple solid state regulator with a couple of simple parts you can get at radio shack. Let me know if I can help you with that.

Thanks remco I had bought one
From a vintage sIte that only makes schematics.Andismade for my truck.

Tester I have a spare original gauge . I may try that first.

Ah, and you have it working with that new regulator?
It surprises me that it would smoke with a new regulator…

Nice truck, btw. I love that model.

No I don’t have the regulater yet . I have a whole spare cluster for the truck that has a extra regulater on it.I may try that though. They do sell new ones for 40+ .