My ammeter goes down,when revs go up.--I've checked base voltage to be `12.5v/...........no load-idle is `13.8v/........load test shows same.....so I beleive system works fine,but the ammeter instrument goes down when I rev up!!--anyone know the fix???...........thanks!!

 

Uh, turn it around? Seriously, is it hooked up backwards?

 

Yeah, the connections are reversed.

 

A good way to double check that the connections are correct, is to turn on the headlights and some other electrical loads with the truck not running. The amp guage should go to the negative side.

 

........I got out there finally and put on the headlights/heater/wipers/fuel pump/interior lights and saw imperceptable difference on the guage.I've got a brand new top-powered battery so it makes sense,I guess. A test voltmeter went from 12.9 to 12.1volts-------I guess I'll try a older battery?!?

 

The ammeter reads current flow, so the battery condition won't matter unless it was so dead it didn't put out anything.

I can't remember what kind of guage you have, but if you have the original Ford guage, don't worry about it. They are famous for not giving any useful info.