Wtf
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More Turbo
Joined: Sep 2011
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Wtf
Ok I will say I’m not the sharpest tool out here. I hooked up my fuel gauge and got it to work with my new stock sender unit. So I went back two days later started my truck and smoke started coming out of the dash. Ss I turned off my truck took off the battery cable. Then took off my dash and traced the melted wire on my fuel gauge and it led to bare wires. Granted this wire harness is 35 years old but it doesn’t make sense. So I took off the bad wire and left the other wire turned on the ignition and nothing. Then hooked up the repaired bad wire to the green and black wire per instructions and it smoked. Am I missing something? I am going to take out my stock gauge and test it. This is what baffles me it worked two days ago no problems. I’m thinking something is shorting out but need advice.
thanks
jerry
thanks
jerry
Senior User
Joined: Jul 2019
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The good news Jerry is that the wiring on a fuel gauge/sender isn't particularly complicated, so I'm sure you'll figure it out quickly. It has to be a short of some type to melt a wire like that. I pulled out my manual to look at the wiring diagram, and I realized I don't know what year your truck is...that makes a difference! 
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More Turbo
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1955 ford f100. I think it’s a bad ground. I’m going to leave the orange wire on the post it is now. And run a ground wire to the truck body. Does this sound right? I started thinking it was wired wrong but it worked before so I think the postage correct. But I am going to pull gauge and check it. I forgot to ask there is a thin metal bridge between the posts. It broke when I was cleaning it does anyone know what this is for?
thanks
jerry
thanks
jerry
Senior User
Joined: Jul 2019
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A bad ground would make nothing happen, as in the gauge wouldn't work, but nothing else would happen either, so while it's entirely possible you do have a bad ground and all, a short is caused by a hot wire grounding itself in some way.
I'm guessing here, but I'm thinking if you just hooked everything up that it's possible that there's some sort of short in the gauge itself or there must be another wire crossed someplace.
The easiest way to chase wiring problems is to disconnect everything, and start testing things one at a time. Pull the hot wire off the gauge, turn the key on and test for power to the wire. If you get power, and no short, then it's not everything between the battery and where that wire is in your hands. If it shorts when you touch it to the connection on the gauge, then it must be something to do with the gauge, or you're touching the wrong connection, as in grounding the hot wire on the ground connection.
There are only a couple of wires, so it should be pretty easy to figure out which place is causing the problem.
I'm guessing here, but I'm thinking if you just hooked everything up that it's possible that there's some sort of short in the gauge itself or there must be another wire crossed someplace.
The easiest way to chase wiring problems is to disconnect everything, and start testing things one at a time. Pull the hot wire off the gauge, turn the key on and test for power to the wire. If you get power, and no short, then it's not everything between the battery and where that wire is in your hands. If it shorts when you touch it to the connection on the gauge, then it must be something to do with the gauge, or you're touching the wrong connection, as in grounding the hot wire on the ground connection.
There are only a couple of wires, so it should be pretty easy to figure out which place is causing the problem.
Fleet Mechanic
Joined: Mar 2007
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From: northeast Ga
If the harness is 35 years old you might think about replacing the complete harness , if you are smoking wires , you don't have fuses . wiring harness kits are cheaper than burning up your truck , and are not hard to instal
Elder User
Joined: Apr 2016
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Like Matt Js 54 mentioned, there is a short causing the wire to burn. Typically a short to ground and too much current passes through the wire. I cannot determine from your original post, is the melted wire the one from the fuel gauge to the sending unit?
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More Turbo
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Ok I agree with all of your replies. I think testing should be the gauge should be tested to see if it works. And the test switched power should be checked. If the gauge is a 6 volt and the truck is switched to 12 volt do I need reduced for voltage to the gauge? I’m going to test the gauge now
thanks
jerry
thanks
jerry
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Yes, reducer is needed when in service on a 12VDC converted vehicle. If you applied 12VDC to the gauge, it could be smoked already. If you have the Ford service manual, procedure for testing the gauge is to apply 1 D Cell battery (1.5VDC) to the gauge and it should read 1/2 way. You can then take 2 D cells in series (- +)(- +) and apply the 3VDC to the gauge and see if read all the way.
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More Turbo
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Ok I traced bad wire until I found good wire. I cut and spliced good wire so I could test. I did the two d battery test and gauge moved. So I asssume the gauge is still good. Bad thing is I started finding bare wires as I unwrapped electrical tape covering the wires. This really concerned me because if I can find bad wire here what else is lurking. I found that I don’t have smoking problems but the bad wiring concerns me enough to buy a new harness. Does anyone know or recommend a wiring harness?
thanks
jerry
thanks
jerry
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For sure, once you start unwrapping that old tape, you start to see things. I replaced my bad wires one at a time, so I didn't get a harness. Doing it this way really taught me how the truck is wired, which was part of my thinking when I did it. You mentioned that you have 12 volts now, I'm going to assume that its 12 volts, negative ground, and an alternator? If that's the case, a generic harness will give you what you need, and you get to choose things like additional power outlets for USB, audio, etc. If you're comfortable with what goes where, a generic one might be cheaper. If you need things to say this wire goes to that, I'm sure there are harnesses out there specifically for your application, and others will chime in who have used them.
The one piece of advice I can give you is to take the seat out and lay a packing blanket or something on the floor before starting the work. WAY easier to work under the dashboard with the seat out, comfortable, even!
The one piece of advice I can give you is to take the seat out and lay a packing blanket or something on the floor before starting the work. WAY easier to work under the dashboard with the seat out, comfortable, even!
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