alternator charging but battery flat after 1 mile


Asked by Jul 28, 2014 at 04:40 PM about the 1963 Ford Thunderbird

Question type: Maintenance & Repair

1963 thunderbird, the alternator is charging and has been checked as ok, it runs the car and can go up to 16 V when I rev, If I start the car with a fully charged battery ( on charge overnight) it runs ok but when I stop a couple of miles later it wont start again, no power.
I have a spare in the trunk and it starts fine on jump leads.
any ideas.
When I put a tester on the NEG post in between the NEG post and the NEG line I get a 12.67 V reading, start the engine , stop it again and I then get a 5.9V reading

5 Answers


First of all a voltage reading of 16 volts when you rev it is too high, the regulator should hold it at around 14.2 to 14.7 volts, voltage like that could fry things like instruments, lights batteries,etc. Did you have the battery checked for proper load capabilities? Make sure your cable connections are good on your battery and engine.

1 out of 1 people think this is helpful.

Thanks tenishoe ill check the regulator and see if I can set it 14.5 max then, if not ill get a new one, ill post the result neil


Tennisshoe thanks for the advise the regulator was adjusted and I turned it down at tbe moment ive left it at13V Im aware this is too low but im now investigating if the previous setting (which I tried at 4000 revs and went to 17.8) ) Was burning the battery hence not holding its charge for this ive put a different battery on.


You also need to have your battery checked for load. Go to any parts house like Auto Zone, Advance Auto, etc and they will check it for you and give you exact info on state of the battery. I had a similar problem and it turned out the battery was bad and it was running on the alternator.


Thanks oldtimer37, between you and tennis shoe I think Ive solved the problem. I had a new battery 1 year ago, then last week on tennis shoes advise I checked the regulator, sent to America for a new one fitted today, voltage now about right (14V) earth wiring checked, Alternator checked by garage and hey, ( battery burnt out) so it looks like the 16-18V on the faulty regulator was the culprit ( and costly) so ill get a new battery. 1 new battery 2 Checked alternator 3 new regulator 4 earth connects show no Voltage drop Thanks again, keep helping im nearly at the end of finding a faulty "knocking" from the front end, next week into the garage again for:- New link bar ( drag link) new inner and outer rod ends new shock absorber from US new shock lower mount Thanks Neil London UK

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