fuel guage weirdness

[Carl Anderson]

Whenever I turn on my lights, the gas gauge reads MORE than what is correct. I seems to be right when the lights are not on, or at least close. Have I got a ground connection going bad somewhere? Where?

[philinjax]

I think your voltage regulator is kicking in incrementally when the system voltage drops incrementally as a result of the current draw when you turn the lights on. The difference between the incrementals here is that the voltage regulator kick-in incremental is slightly greater than the voltage drop incremental caused by the the lights turn on. Therefore, the voltage accross the fuel level gauge is increased by the differential of the incrementals resulting in a reading that is greater. All clear?
Phil

[philinjax]

Ooops, I forgot to mention that if the voltage regulator is exchanged for another, especially a solid state regulator, it will likely fix the problem.
Phil

[Dave at Pelican Parts]

I wouldn't be surprised if simply cleaning every connection in both the headlight circuit (and the "parking light" circuit, and all the other circuits fed by those circuits!!) and also the fuel gauge circuit cleaned this problem up.

Mine does the same thing... I have a solid-state regulator. I haven't bothered to clean all of those connections I mentioned.

--DD

[philinjax]

Cleaning contacts and connections in electrical circuits as a method of correcting problems is highly overrated. It can not in any way replace systematic trouble shooting however, it is good housekeeping.

Phil

[Zeke]

Originally posted by philinjax
Cleaning contacts and connections in electrical circuits as a method of correcting problems is highly overrated. It can not in any way replace systematic trouble shooting however, it is good housekeeping.

Phil

I couldn't disagree more. While part of what you say is true about cleaning not replacing diagnostics, without good and proper grounding, you won't get appropriate readings for diagnostics. A little "housekeeping" is extremely important before advancing to diagnostics.

[philinjax]

Zeke, You are in the right ballpark but, understand, systematic trouble shooting will, ultimately, uncover all faults, including faults associated with lack of good housekeeping, i.e., why put the old horse before the cart, making him expend all that time and energy plodding down the track of cleaning contacts when he could be using simple trouble shooting logic to go directly to the fix, even the fix that might uncover a bad connection? Just my opinion.
Phil

[Carl Anderson]

Thanks for the inputs, guys. I think I'll try some of all the advice- the car sat for a long while before I got it, so cleaning contacts is cheap and probably a good way to avoid future funny business, even if it doesn't fix this.
Systematic trouble shooting is also something I can do. I can measure and see if the voltage is changing with the lights turned on. I don't think I'll just go buy a regulator and hope that's it.