Wiring a mini voltage meter

[cmyoch]

I purchased a 3 wire mini voltmeter on eBay. I hooked red to hot, black to ground, and left the white alone. The gauge lights up but doesn't read anything. Am I missing something? I'm not an electrical wizard so I'm sure it's something simple?

 

[wannabridin]

I would assume the white would be the voltage pickup. That would need to go on a voltage-supplier wire, maybe for your headlight power lead or similar.

 

[XSLeo]

Red = hot sounds good. black = ground, maybe not, The white maybe ground, the black might have to connect to the head lights hot wire between the on/off switch and the dimmer switch. This way when the headlight is off, you get a bright back light for daytime running. When you turn on the headlight, the black wire sences headlight power and the display dims for night time.
A lot of car radios are set up this way. I had an old Supra that the clock worked that way. I figured this out when I swapped in a digital clock for the analog one. Decided I liked the anolog better and swapped back.
On your 78 does it still have the headlight switch? And does it turn the headlight of/on? If so wiring it the way I described should work ok.
Leo

 

[chizler62]

White is probably key hot. Theoretically it would drain battery if left hook up reading continuously.
Red directly to positive post. Black directly to negative post.

I've always been confused as to why people insist on reading voltage not amps

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[TwoManyXS1Bs]

I purchased a 3 wire mini voltmeter on eBay. I hooked red to hot, black to ground, and left the white alone. The gauge lights up but doesn't read anything. Am I missing something? I'm not an electrical wizard so I'm sure it's something simple?

That's actually the better voltmeter, has reverse bias protection.

Red is the power supply
White is the voltage measurement
Black is ground

Simply tie the red and white together, connect them to brown switched power.
Black to ground.

 

[cmyoch]

That's actually the better voltmeter, has reverse bias protection.

Red is the power supply
White is the voltage measurement
Black is ground

Simply tie the red and white together, connect them to brown switched power.
Black to ground.

My other meter was analog with two connections. I played around and wired the Red and White together and it works perfectly! I must say that this was the best $5 I had spent in a while. I'm studying the best mounting options for it now.

Thanks for the help guys!

 

[TwoManyXS1Bs]

Several of the guys show some neat and clever mountings in my old voltmeter thread:

http://www.xs650.com/forum/showthread.php?t=27151

I used the 2-wire digital voltmeter in that thread, but it recently 'patooied' on me. It couldn't handle the occasional negative voltage produced by alternator inductive kickback.

I have several of the 3-wire units, noted as having reverse-bias protection, and replaced the failed unit with one of them. Works fine, just a bothersome 3rd wire to deal with.

I've seen some newer 2-wire versions available now with this protection, and those should be used instead of the older versions...