Yesterday, I helped a guy rewire his 1924 T Pickup that had a wiring fire and ammeter melt down.
Naturally I suspected the usual problem and found another ammeter for him, not an easy task now days.
He had the small upgrade and I found an original.
I had previously tested the ammeter by running 6 volt current through it in both directions from a battery to a head light bulb.
Everything looked great, but I told him that it was hard to tell if the ammeter polarity was correct, unless we turn on the lights and see a discharge and then see a charge when the engine is started and reved up some. Some times the wires have to be reversed!
When I connected the battery, with the light still off, I got a big spark and the ammeter pegged past +20.
I immediately suspect the starter switch was shorted and removed the wire to the terminal block.
Then, there were no sparks when the + terminal was connected to the battery.
There were no shorts on any of the other wires either.
The wires were connected again and the engine was started.
The ammeter showed just a very faint charge with the engine reved up some.
The ammeter showed a normal discharge when the lights were turned on, and everything worked normal.
We did determine the cause of the fire was the generator to ammeter wire was shorted to ground by being out of the usual routing and under the hood edge.
The ignition switch was rebuilt and passed inspections.
What could peg the meter in the opposite direction is a big mystery yet.
The real question is, "have all the problems been found and repaired?"
A Weird Ammeter Problem
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