Alternator Not Charging Battery

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fiat76
Posts: 2
Joined: Mon Nov 17, 2014 11:23 am
Your car is a: 1976 Fiat Spider

Alternator Not Charging Battery

Postby fiat76 » Tue Jun 27, 2017 1:49 pm

1976 Fiat Spider 124
New battery
Alternator looks fairly new

The alternator is outputting 15 volts, but it is not charging the battery. First, is there a voltage regulator; and, if there is, where is it located?

baltobernie
Patron 2020
Patron 2020
Posts: 3466
Joined: Sun Nov 25, 2007 6:00 pm
Your car is a: 1973 Spider [sold]
Location: Baltimore, MD

Re: Alternator Not Charging Battery

Postby baltobernie » Tue Jun 27, 2017 8:20 pm

First, many Spiders have had electrical items replaced with different items than were originally provided. A few photos of the engine bay, and a close-up of the alternator would help us diagnose your situation.

Have you followed this procedure to test you system? https://www.yourmechanic.com/article/how-to-test-your-alternator_2
What were your readings under the three conditions described in the test?

gchocevar
Posts: 108
Joined: Tue Oct 21, 2008 9:40 pm
Your car is a: 1979 Pininfarina 2000
Location: Cleveland Ohio USA

Re: Alternator Not Charging Battery

Postby gchocevar » Tue Jun 27, 2017 9:55 pm

Baltobernie posted a good quick check for an alternator. Mine was overcharging the battery in that acid was starting to drip out the caps.

My problem was two-fold on my 1979. The regulator was bad. It is incorporated into the alternator. You may need to remove the alternator to remove the regulator unless you like working in tight spaces on your back. It's an easy bench replacement.

Secondly, you could have a good clean ground in the trunk, but the engine block is grounded through the transmission with a wire that runs from it to the tranny housing. It is very close to the side where the gas pedal would be, My ground was hanging on three wire strands and bolted to a rusted out floor. The other strands were broken or corroded. I bolted a new one in place after welding in a new floor during the restoration.

Good luck!
Greg


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