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Posted by David Sherman [72.47.9.228] on Tuesday, January 11, 2011 at 13:24:25 :
In Reply to: fuel gauge sender posted by David N. Lundstrom [209.62.224.1] on Tuesday, January 11, 2011 at 10:59:26 :
I've seen too many 6 volt fuel gauges burned up because somebody did that. The "dropping resistor" will work somewhat and will at least save the gauge, provided you use the right value, which I don't know off hand. What's better in terms of maintaining the original accuracy, such as it is, is an actual voltage regulator, since the amount of current the gauge draws varies depending on the float position. I believe JC Whitney sells both the "dropping resitors", which I wouldn't trust to work very well, and a little plastic blog with leads coming out of it, which is essentially an LM7806 regulator. When I rewired my 12 volt sno-cat, which by some miracle still had 6 volt gauges that weren't burned out, I built a rather excessive 6 volt regulator to power the gauges. I used an LM317 with a suitable voltage divider because I didn't have a 7806 on hand, and put a whole bunch of protection around it (backwards diodes at both ends, and back to front, and a resistor at the input followed by a zener, plus some capacitors) to protect it against every imaginable electrical spike including hooking up the battery backwards, and put it in a waterproof box. I was tired of half-assed maybe-sorta-sometimes-work solutions and decided to just give the guages the cleanest 6 volts they've ever seen and let them work better than new.
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