Quote:
Originally Posted by kgschrader 
I've checked. It is not overcharging, it's just that the ammeter is showing every amp drawn instead of just what is going to the battery charge, as is typically what is shown.
Turn the lights on and the ammeter jumps to the right.
Turn the A/C on and it jumps even more to the right.
To the point where the needle is buried and you can't see it.
No other problems exist, the battery is fine, the alternator is fine, etc. etc
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Still confusing, if you don't have a Superformance sitting in front of you.
Is 'to the right' towards the positive (charge) side or negative (discharge) side?
All the car electrical draws should be on the negative side. With the key on, motor not running, actuating anything electrical should result in a discharge indication (which is normally the needle moving to the left). With the key on and the engine running, the needle should be showing a slight charge at anything above idle rpm. Increasing electrical load (say, by turning on the headlights, or the A/C) should initially result in immediate movement in the direction of discharge (perhaps not into the negative region, but at least movement in that direction), followed instantly by the needle returning to its slight charge position as the voltage regulator steps up the alternator output to compensate for the increased draw.
Your description makes it sound like both the load and the charge wires are hooked to the same side of the ammeter. This would cause the needle to move towards the positive side whenever there is power applied (that is, the alternator is charging) and move even further to the right when a load is placed on the system.
That ain't right!
I can't comment on the construction of the SPF ammeter itself, but it sounds like there are better GT40-correct ammeters available out there. I'm not sold on the idea of a voltmeter being a better substitute, because although it shows total electrical charge available, it doesn't actually show that the charging system is really functioning. Your alternator could quit, and the voltmeter would just slowly drop, which would be difficult to discern. When an alternator quits, an ammeter shows a pronounced discharge when an electrical load is produced, which is quite apparent right away.
I was photographing a Pantera last weekend; the insulator inside the alternator gave out and shattered, and pieces of it jammed the stator, locking up the alternator solid for a few moments at a time before the piece of debris would break. Besides the smell of burning rubber and the sound of a belt slipping, the ammeter told the tale right away, whereas a voltmeter wouldn't have shown anything significant.