adding a voltage gauge (1980)

[scampbel98]

I'm adding a voltage gauge. I want to pick up alternator output voltage.
I don't think I can use the blue/black off the alternator that drives the charging light.
Thoughts???

Already have the gauge

[burgandy81]

I wired mine (VW triple gauge set) into the regular harness at the gauge panel as described on a VW site.

My understanding is that the system voltage is the Alternator output voltage. I reads approx 11V not running, 12-13 at idle (no accessories) and approx 14 above 1500 rpm. This is what I expect from the alt.

Anyone who knows more have a thought?

[hayesbd]

I found a large red LED volt meter at Walmart and adapted it into my ashtray. Under normal circumstances, the ashtray is closed, but when flipped up it turns on the meter. It's nice having an indication of how the voltage regulator is working since I still have the original mechanical style regulator that occasionally needs a whack to get it to stop overcharging.

Brian

[spider2081]

Yes you could use the blue/black wire that feeds voltage to the charge indicator light. That wire has voltage on it when the ignition switch is in the start or run position. It is not protected by a fuse so if your wire to the voltmeter ever shorted to ground your wires could burn. I would connect it to one of the fuses that have voltage in the run position of the ignition switch.

The charge indicator light works by having voltage applied to one side of the bulb. the other side of the bulb is the field voltage to the alternator. when the alternator is not spinning the light will light through the field winding and voltage regulator to ground. lighting the light. When the alternator is spinning the regulator opens the connection to ground and the light goes out.

[spider2081]

sorry this was a double reply

[focodave]

I replaced my non-working clock in my 1980 with this voltmeter I bought at O'Reilly's Auto Parts.
It was a perfect fit in the original hole.
I wired it to the headlight switch and used the old clock light wire for the voltmeter light.

[scampbel98]

Thanks

[bradartigue]

Veglia made them:

http://www.ebay.com/itm/like/110734745386?lpid=82

The one above is for a Jaguar. They made the same gauge for a bunch of cars, but the Jag one matches most closely the FIAT dashboard. There is also a red one with a grid but it's a bit futuristic looking for the 124.

[baltobernie]

I don't think I can use the blue/black off the alternator that drives the charging light.

Don't install anything in the path of the charging lamp circuit; it may affect the operation of the alternator.

Any other location of 12v is acceptable for tapping. I used the cigarette lighter wire.

[spider2081]

On my 1981 the cigar lighter is "voltage all the time" so even with ignition switch off the voltmeter would be indicating and drawing down the cars battery. A very small draw but still a current draw.
Also on my 81 connecting to the blue/black wire of the charge indicator light is the same circuit as Fuse B for windshield wipers and heater as well as feed wire for headlights, radio and power windows. This wire is voltage in "run" position of ignition switch only.