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electrics question
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tatcat
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PostPosted: Fri Nov 21, 2014 8:43 pm    Post subject: electrics question Reply with quote

new alternator in
all good 14.5 at battery and gauge
when i turn on the lights the gas gauge needle flips over to full and the voltage gauge shows 13.
car has always done this even with old generator.
just using a two way toggle switch, up headlights, center off, down running lights.
should there be such a drop in the voltage?
would a better switch and perhaps a relay remedy the situation.
perhaps a wiring diagram for the relay?
thanx
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jspbtown
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PostPosted: Fri Nov 21, 2014 9:16 pm    Post subject: Reply with quote

Sounds like a bad ground and a potentially dangerous situation.
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bruces
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PostPosted: Fri Nov 21, 2014 9:23 pm    Post subject: Reply with quote

Is the car running or not?
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Dale M.
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PostPosted: Sat Nov 22, 2014 8:30 am    Post subject: Reply with quote

Might be bad grounds or wire gauge is to small from battery through switch to headlights (or ground wires) ...

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EVfun
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PostPosted: Sat Nov 22, 2014 9:31 am    Post subject: Reply with quote

Speedometer is not grounded. With the lights off it finds a ground through the speedometer light bulb, to the headlight switch, to the headlights, through them to ground. When you turn the lights on that ground path is eliminated and the gas gauge voltage regulator can no longer function. This causes the gas gauge to get full voltage instead of about 5 volts, so it swings hard to full.
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tatcat
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PostPosted: Sat Nov 22, 2014 9:47 pm    Post subject: Reply with quote

EVfun wrote:
Speedometer is not grounded. With the lights off it finds a ground through the speedometer light bulb, to the headlight switch, to the headlights, through them to ground. When you turn the lights on that ground path is eliminated and the gas gauge voltage regulator can no longer function. This causes the gas gauge to get full voltage instead of about 5 volts, so it swings hard to full.


this is where i was going to start looking.
i'd seen a video about a gas gauge sending unit that mentioned a regulator on the speedo.
any help on the location or description of the regulator.
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EVfun
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PostPosted: Sat Nov 22, 2014 11:11 pm    Post subject: Reply with quote

The gas gauge voltage regulator is a small can mounted on the back of the speedometer near the top. It is likely fine, but you will need to pick a screw on the back of the speedo (perhaps the one next to to the one holding the voltage regulator in place) to attach a ground wire. The speedo uses the dash attachment for ground in a Bug, but fiberglass doesn't offer that grounding in a Buggy.
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clonebug
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PostPosted: Sun Nov 23, 2014 9:24 am    Post subject: Reply with quote

On a buggy everything needs a ground. I have my speedo grounded and I have a mechanical fuel gauge.
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