When I first bought my Mach, lo some 30 years ago, the Ammeter wouldn't move either way, charge or discharge. I was working at a shop, and the owner had a look at it and told me , wiring-wise, it was hooked up correctly. I guess it's just a bad guage, but I've never replaced it since I bought the car. I'd really like to replace the whole 3-guage set-up with some matching AutoMeter red-orange pointered , factory appearing guages. To do so will require some adaption, and I just don't want to stop driving it to do the adaption , just because of that. The Oil Pressure and Temp guages , in that trio, work fine. One of the advertisers converts the Amperes guage to a factory looking Voltmeter. I kinda like that simple modification.