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Okay, I had to take my Mayfair to a wiring guy. She sat all day, after work, I went to leave and she refused to start. So I had my son come give me a jump and asked him to follow me home.(converted to 12V before I bought it) I live ten miles from work. He had to jump me six more times to get home, every time he put the negative cable on the post, fired right up, I would start to drive and it would just die, no heads up, no crazy noises, just shut off like someone turned the key off. As soon as I pulled in the driveway and shut it off, wouldn't restart. I called around and found this local shop suggested by some friends. I put the manual in the front seat for reference. He called and said the alternator was dead, not charging at all. So he replaced it, and I called yesterday afternoon to pay the bill, and he said that didn't take care of it. Any ideas?? Anybody else out there had this issue before? Thanks as always in advance! I mentioned to him about the small fire and the location too. He was really stumped by the positive ground! Anything helps guys, thanks!

I had a similar failure a few years back with my 56 V8. In my case it was the points that caused the sudden failure. Not exactly the same as yours but it did quit without warning and would not restart and had to flatbed home. Good luck.

When you say "refused to start" do you mean it was completely dead and wouldn't even turn over? Or would it turn over but not start? Turn over slow and not start?

It started okay when you went to work?

It seems like something is shorting out. Even with a dead battery, once the car is running it should keep running. Maybe your battery has an internal short? You could get it tested, or swap it out, just to eliminate that possibility.

Fire? I think I missed that post. What was this fire? This seems like something that warrants investigation.

If the positive ground stumped him, you might have to find an older mechanic! LOL

I'm not a fan of 12 volt conversions.

we are alike in that sense, I hate conversions too, 6V is just fine, just have to be more mindful and that is why most folks hate them, don't want to be bothered! But, that was done before I bought it. It ran perfectly on the drive to work, everything, OD engaged, no issues, I got to work. When I came out at the end of the day, the idiot lights came on when I switched the key "on" but it would not turn over at all. The wiring guy tested the alternator and it was dead. So he replaced that. Still not starting, idiot and interior lights come on. So, one of the issues WAS the old alternator, but after replacing that, still the same, turns on will not turn over. Same car that had the small fire, yes. And thanks for the quick responses, I'm going to call the wiring guy at the end of the day and let him know what ideas were offered up. I did explain about the fire and the location. Also looking at getting a tach and temp gauge installed. Might go back to 6V too if I'm feeling spunky!

Your battery may be discharged or defective. It's possible a battery issue caused the alternator to fail, or vice versa. I'd charge the battery overnight and see if the car will start. Is you car still positive ground after the 12 volt conversion? Most are not. I don't think positive ground alternators are very common, either, so there may be an issue there. Generators can be made to charge either positive or negative ground, but I don't think alternators can be.

A failed diode can allow an alternator to discharge a battery. That might explain the original no-start situation, or the alternator may have failed for any reason and the battery simply ran down. Most all alternators are intended for use on negative ground systems, and replacing an alternator adapted for positive ground use with a "normal" one intended for negative ground use will cause problems.

12 volt conversions usually give more trouble than they're worth. Problems can arise with ignition systems, starters, radios, dash gauges, and more. Many, if not most conversions are not done correctly.

The guys charged the battery, it is holding the charge

I agree, might have to switch it back

In post 4 you said idiot lights are on but it won't turn over. The alternator should have nothing to do with the start circuit as that would be primarily a problem with the battery, a cable, ignition or starter switch, starter solenoid, or the starter motor.

When it suddenly stops and there is no sputtering or low gas symptoms beforehand then I would start thinking that it was a failure in something supplying or enabling the spark. If so, could be a broken or loose wire, a hot component such as the coil, condenser or ignition switch that heated up and opened the circuit. Do the idiot lights immediately come on when the engine quits? Since you have an overdrive you also cannot rule out something in the OD kickdown circuit is possibly shorting the coil out long enough to kill the engine.

When you said it was able to start after a jump, how long was the delay? If it was long enough for something to cool down then a failing coils is notorious for that symptom. Condensers too but usually when those fail, it is a hard failure but it is possible it is getting hot and a connection is opening rather than shorting. That could cause problems with the points buring or oxidizing enough to kill the spark but if that happens it is usually a hard failure too.

Did the conversion include a ballast resistor in the wire feeding the coil coming from the ign switch? Trying to run a coil on a full 12v usually results in a very hot coil so unless they also added a resistor in the feed or changed to a coil having an internal resistor I would start there.