I was driving the bird back form the alignment shop (only its third test drive since redoing it for three years) and the 50 Amp Maxi fuse blew. Obviously the car stalled. So I picked up another fuse put it in, charged the battery and it blew again. I watched the voltmeter after it blew and it was off the charts (pegged to the right)! Before it blew it was steady at about 14V (while driving).

During my resto I removed my voltage regulator and installed an internally regulated alternator. Could the alternator be bad? Could the alternator be bad because I wired it incorrectly? The car drove to the alignment shop fine . Would it drive 8 miles with incorrect wiring?

Thanks, Ryan

Ryan,
Check out your main power wires to the starter. Since it happened after you were driving for a while I'll bet you have a wire touching metal.
Jim

where is the maxi fuse installed? what does the power go to after it? What year is your bird?

"Would it drive 8 miles with incorrect wiring?"

Yes it would, until heat, resistance and amps build up to a point where it causes a melt-down ( or in your case the blown maxi-fuse. Need to check all primary wiring from battery to starter to alternator first. Then work on the smaller, lesser important links.

Are the battery connectors clean, new and showing no signs of over-voltage? Burnt or soldered appearance? When I converted to HEI ignition I did not disconnect one very small but important wire to the starter. This caused the starter to remain "hot", car drove fine for two or three neighborhood test drives. However, when I took it out for a longer test on the highway the heat and amps built up to the point where the positive battery connection melted off completely. It was not pretty, but this website nailed down what wiring errors I had made.

The Maxi fuse is installed after the starter and before the main fuse box. I don't have any thing to draw current. No radio yet, no power top yet, lights were off. I looked at all the wiring from the battery to the starter and to the main fuse box. Nothing seems loose or burnt. The starter, alternator, battery and 100% of the wiring is all brand new, but I think the alternator is defective. I have taken it off and will exchange it for a new one (warranty). I let you know what happens.

Let's not confuse amperage and voltage. Your fuse USUALLY won't blow because of overvoltage. Granted all fuses have a voltage rating, but your voltage regulator USUALLY won't produce enough voltage to burn up the fuse element. Notice I say "usually", because there are no certainties in electricity.

I've seen fuses run on voltages well over 1000% of their listed rating.

Fuses blow from an overcurrent condition. And Jim is probably right about the short-circuit. A short circuit draws incredibly high amperage. For instance, a short-circuit in a 120 volt receptacle will often pull 35,000 amps. Chances are your fuse is blowing from a short someplace. And yes, that short could be inside your alternator - possibly the windings are going to ground.

There are lots of other possibilities, so let us know what happens with your alternator test. Do you know how to determine if you have a voltage leak to ground with the ignition off?

- Jake

Oh yeah ... voltage and amperage are inversely proportional. If your voltage goes high off the scale your amperage will go low off of the scale.

- Jake

I replaced the alternator, which had a lifetime warranty and drove around for about 10 miles. It seemed to run fine. I wanted to start off slow so I didn't run it very hard. The problem was that the first alternator wasn't putting out any voltage, but I don't know why that would blow the 50 Amp fuse. Maybe there was also a short in the internals???

Thanks for the help, Ryan

Because voltage and amperage are inversely proportional. Let's say you have a 12 volt load that pulls 10 amps (a blower motor perhaps). If your alternator is only putting out 2 volts the blower motor will pull 60 amps and knock out the fuse.

People mistakenly think that low voltage underpowers specific loads and therefore pulls fewer amps. Not so.

- Jake