[eamonford]

My Model A is running a 12V system, with a 60A alternator using the one-wire setup. I recently replaced the coil, and added a ballast resistor. The next time I drove, the car ran fine, but when I hit about 50mph, the headlights blew out and a few miles later, the starter fuse blew. I disconnected the horn/lights wire from the alternator and replaced the fuse, and drove again — after a few miles and when I had been going 50mph for about 30 seconds, starter fuse blew again. Thought it might be a short in the ammeter, so I removed the ammeter and temporarily spliced the wires together (also disconnected the instrument light). But the fuse blew again after a few miles and 30 seconds of driving 50mph. Later after replacing the fuse I tested the voltage at the alternator BAT post while idling, and it was a steady 14.5V. I should note that before removing the ammeter, it would read 30A when I drive 50mph, and these are 20A fuses. So that seems like a problem... but why is the alternator putting out that much current?

But here’s something important: each time the starter fuse blew, the engine cut out. Shouldn’t the alternator be supplying power to the ignition system? As an experiment, I removed the starter fuse and tried hand-cranking the engine, and it did not start. Does this mean something’s wrong with my wiring? I have the starter fuse connected in between the terminal box and the post on the starter.

Thanks very much.