Join Date: Nov 2002
Location: Ontario & Oceanside CA.
On a 69. This gauge is normally attached with the black wire to the power terminal behind the battery, and the other wire, a black with a white stripe to the same wire that comes off the alternator (the big red one that feeds a charge to the battery) but it is connected to this wire just upstream or before it reaches the voltage regulator. So it measures a charge if the alternator is putting out more than battery voltage, or a no charge if the alternator is putting out less than battery voltage. The ground wire is a small gage 16ga. or 18ga. for the console gauge lights only. The best way to test this gauge in my opinion, is in the car. Just hook up a set of cables to a known undercharged battery and observe the gauge. Putting lights on high beam and turning the headlights on and off will also cause the gauge to operate. It didn't move much anyway.
A real amp gauge has ALL of the vehicles voltage flowing through it. (except the starter). It is connected in series with the wire that comes off the battery to feed power to the whole vehicle. These types of amp gauges were replaced with the safer style you see on the early Camaros. Vehicle fires were responsible for this change. Just about every manufacturer that puts gauges in a car today, uses a volt gauge. (sometimes labled a BATTERY gauge) These are a much easier gauge to install, are more usefull and much safer.
Hope this helps.