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Alternator question..


Well-known member
Aug 26, 2012
Austin, TX
I'm not sure that this is the right place, but I have an alternator question..

I've redone several Mustangs in the past, and I always made modifications to the alternator. In my '67 I went with a late model set up. In my '66 I went to a 1-wire set up. Here's the story..

In my CS, I'd like to keep it period appropriate, but I'm not sure that the alternator is putting out enough "juice". Last night I took the car to dinner. By the time I returned to my driveway, the car died and wouldn't restart. It was obviously a weak battery. I charged the battery and ran some diagnostics today.

At 1900 rpm the volt meter read about 14.58
At idol, a little lower.

When I applied a load of A/C, radio, headlights, and fog lights, meter read about 13.48, which would appear to be plenty.

I then shut the car off and re-tested battery. It still read 13.48 volts. While I realize that this is a garage mechanic version of a test, here are my questions.

1) what is the proper voltage at full load and idol?
2) in my situation, should I expect more?
3) are there any options for remaining period correct, but getting a bigger alt?

I'll probably pull the battery this weekend and have it tested, but I always like knowing what others think.