[Grandma’s 68]

Further developments. I disliked the idea of working on behind the dash wiring, so realized I can start with the disconnected bulkhead connector.

I first measured the resistance, expecting to see it was a failed open circuit. It wasn’t. It measures 1.8 Ohms, which doesn’t seem very much, but I’ve no idea.

I then hooked up a regulated power supply and put in 0.5V. The gauge moved! It seemed to take about 0.48Amps to move it. I turned the supply up to 1.0V and the current was 1.1Amps. I swapped over the wires and the gauge also worked in the other direction. With 0.5V it took 0.5A and at 1.0V it took 1.2Amps.

Previously I measured the current flow from the alternator to the battery and it was 0.2Amps, so there was probably some small movement of the gauge, I just didn’t notice it.

So the ammeter appears to work, but I’m not sure these values are ‘normal’. If they are, it’s just that in normal operation there is almost no discernible movement of the needle. Is that correct functionality?

I’m ready to finish this quest and hope that if the alternator isn’t charging I’ll get some sign on the ammeter.

Thanks for everyone’s help.