After installing new battery and alternator the battery goes dead

1994 LINCOLN TOWN CAR

138,000 MILES • 4.6L • V8 • 2WD • AUTOMATIC

RANDALL729

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I just installed a new 1000 amp battery and a new 130 amp alternator in my car. The battery goes dead. I did test the voltage at the battery terminals of the car not running and this was 12.4 volts. With the car running it showed 11.9 volts. I seem to think the reading should have been 14.2. The alternator may be the problem but not sure? There is a guarantee for replacement of the alternator or if it may be the battery there is a 30 month guarantee. Should I approach the parts store about the alternator? Thank you.

Jul 8, 2019 at 10:44 AM

ASEMASTER6371

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52,796 POSTS

Good afternoon,

You need to do some testing first before assuming the alternator is the issue.

I attached a wiring diagram for you to view.

Check for voltage at the big wire at the back of the alternator. Make sure it has battery voltage. Check the fuse listed for power with the key on.

Check the third wire for power at the back of the alternator.

Roy

Image (Click to enlarge)

Jul 8, 2019 at 11:56 AM

RANDALL729

MEMBER
59 POSTS

Thank you and problem solved. With car running, getting 14.5 volts at alternator, 14.5 volts at under hood fuse block terminal, 14.5 volts at the positive post of the battery. Actually what I did was clean up the post connections good as before the volts were 11.9 with car running. But I also followed your advice.

Jul 9, 2019 at 10:40 AM

ASEMASTER6371

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52,796 POSTS

You are welcome.

Roy

Jul 9, 2019 at 11:03 AM