voltmeter

[Baz]

Anyone know what the voltage should read from the alternator, and can this be measured at the ammeter/voltage gauge across the two wired at back of gauge. My gauge used to read in middle green section, now just shows in the green edge. Battery fine, gauge maybe ??

[spider2081]

I don't know if a 77 Spider would have had a factory installed volt/amp meter. Could this be some after market gauge a previous owner installed?

and can this be measured at the ammeter/voltage gauge across the two wired at back of gauge.

Not knowing what the gauge is you have in the car your question can't be answered. You can measure the voltage out of the alternator at the alternator output post on the back of the alternator when the engine is running above 1500 RPM.

[Baz]

well, it all looks pretty original, and is set up the same way as the other gauges. It has a light in the back with one red wire and a black wire.
as the car was converted to RHD the loom is a bit ordinary but the dash is factory I would guess, but who knows...CAL car....the gauge has a
band of color...small red...middle green and small red on the right hand side. Veglia....
Thank you for the response.
Baz

[18Fiatsandcounting]

Veglia did make a battery gauge, but it was never installed in the stock spiders. Someone could have added it afterwards, of course. The red and green bands don't tell you what the voltage actually is, so for that, you would need to use a voltmeter as spider2081 suggests. Any auto parts store would have a cheap voltmeter, or you can order it online. Make sure to take the measurements using the "DC volts" scale (and not the AC volts setting).

Normal alternator output is around 14.5 volts when the engine is revved up. At idle, it could be less, but it shouldn't be less than a fully charged battery would be, which is 12.6 volts. In other words, with no accessories turned on like headlights, the alternator output should be between 12.6 and 14.5 DC volts depending on engine speed. The voltage should be fairly steady, that is, it shouldn't jump around.

-Bryan

[Baz]

Thank you Bryan.....