What did I do?
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Joined: Jun 2010
Posts: 169
From: Houston, Tx
What did I do?
My fuel guage is doing something strange. When I turn the ignition key to start the guage reads fine however, when I turn the headlights on, the needle pegs past full. Recently,
I took out the speedometer and fuel guage to replace the bulbs and one of the pins on the back of the speedometer broke off and had to be resoldered back on . Did something go wrong with the soldering?
I took out the speedometer and fuel guage to replace the bulbs and one of the pins on the back of the speedometer broke off and had to be resoldered back on . Did something go wrong with the soldering?
Registered User
Joined: Jun 2009
Posts: 15,194
From: southeastern Michigan
I would guess yes. A fuel gauge pegging well past the full mark indicates an open circuit (infinite resistance). Somehow your system is wired so that turning on the headlights breaks the fuel gauge circuit, which is weird.
Power to the fuel gauge comes off of the "instruments" fuse on the fuse block, goes through the gauge and to the sending unit in the tank, and then to ground. The headlight circuit is not any part of this. I think you need to check your soldering to see if you haven't spilled some solder somewhere it shouldn't be or if a too-large blob of solder is causing a short somewhere. Perhaps some solder is shorting to the instrument cluster illuminating lamp circuit. Those go on when the headlights are turned on, and that's the only place I can think of where the fuel gauge circuit comes electrically anywhere near something controlled by the headlight switch.
Or you could just never drive the car at night!
Power to the fuel gauge comes off of the "instruments" fuse on the fuse block, goes through the gauge and to the sending unit in the tank, and then to ground. The headlight circuit is not any part of this. I think you need to check your soldering to see if you haven't spilled some solder somewhere it shouldn't be or if a too-large blob of solder is causing a short somewhere. Perhaps some solder is shorting to the instrument cluster illuminating lamp circuit. Those go on when the headlights are turned on, and that's the only place I can think of where the fuel gauge circuit comes electrically anywhere near something controlled by the headlight switch.
Or you could just never drive the car at night!
Last edited by jaunty75; Sep 6, 2011 at 07:17 AM.
Thread Starter
Registered User
Joined: Jun 2010
Posts: 169
From: Houston, Tx
I would guess yes. A fuel gauge pegging well past the full mark indicates an open circuit (infinite resistance). Somehow your system is wired so that turning on the headlights breaks the fuel gauge circuit, which is weird.
Power to the fuel gauge comes off of the "instruments" fuse on the fuse block, goes through the gauge and to the sending unit in the tank, and then to ground. The headlight circuit is not any part of this. I think you need to check your soldering to see if you haven't spilled some solder somewhere it shouldn't be or if a too-large blob of solder is causing a short somewhere. Perhaps some solder is shorting to the instrument cluster illuminating lamp circuit. Those go on when the headlights are turned on, and that's the only place I can think of where the fuel gauge circuit comes electrically anywhere near something controlled by the headlight switch.
That make sense, The soldering job could have been better if not cleaner but it seem like it got the job done. As for not driving at night, thats not an option with 100+ degree temps down here in Houston, night is the only time I take her out for a drive.
Or you could just never drive the car at night![/QUOTE]
Power to the fuel gauge comes off of the "instruments" fuse on the fuse block, goes through the gauge and to the sending unit in the tank, and then to ground. The headlight circuit is not any part of this. I think you need to check your soldering to see if you haven't spilled some solder somewhere it shouldn't be or if a too-large blob of solder is causing a short somewhere. Perhaps some solder is shorting to the instrument cluster illuminating lamp circuit. Those go on when the headlights are turned on, and that's the only place I can think of where the fuel gauge circuit comes electrically anywhere near something controlled by the headlight switch.
That make sense, The soldering job could have been better if not cleaner but it seem like it got the job done. As for not driving at night, thats not an option with 100+ degree temps down here in Houston, night is the only time I take her out for a drive.
Or you could just never drive the car at night!
[/QUOTE]
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