Battery will not hold a charge

WYOREDNECK

MEMBER
1997 MAZDA PROTEGE

I am trying to fix my brother's car and the battery will not hold a charge. I have replaced the battery twice, the alternator, battery cables, and the main relay. With a jump it will start and run for a few minutes, and all day on the new battery, but then the airbag light starts to flash, and the battery drains.

5 Replies

KHLOW2008

MECHANIC
41,814 POSTS

Hi WyoRedneck,

Thank you for the donation.

The problem seems to be with the charging system. I would suggest testing the charging voltage between battery terminals and between alternator mast and engine ground.

Charging voltage should be between 13.5 to 14.5 volts. If after initial starting, the charging voltage is ok, let it run for a few minutes and recheck. If the voltage drops, it could be due to a faulty alternator, or the alternator is not turning at the required speed due to a bad crank pulley. The harmonic damper could have detached itself causing the problem. You might have intermittent belting noise.

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Tuesday, May 5th, 2009 AT 1:10 PM

WYOREDNECK

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3 POSTS

I tested it I am getting no charge from the alternator to the battery. I had the alternator tested it is good so now what?

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Tuesday, May 5th, 2009 AT 8:21 PM

KHLOW2008

MECHANIC
41,814 POSTS

Is the charge indicator light showing with ignition switch "on" and engine "off"?

Is the charging indicator light showing with engine running?

At alternator main terminal, is there battery voltage with engine off and 13.5 or more volts with engine running? If yes and at battery terminals battery voltage is less than 13.5, the connection from battery to alternator is bad.

Check for a broken Black/White wire connection from alternator to battery. Check the 100 A fuse in main fuse block under hood.

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Wednesday, May 6th, 2009 AT 8:55 AM

WYOREDNECK

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Yes, the charge indicator light showing with ignition switch "on" and engine "off".

Yes the charging indicator light showing with engine running.

Yes, at the alternator terminal there is 13.5 volts.

At the battery terminal it is only 5 volts.

The fuse was one of the first things we changed, and we have replaced all of the wires except the one from the starter to the alternator.

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Friday, May 8th, 2009 AT 1:25 PM

KHLOW2008

MECHANIC
41,814 POSTS

The Alternator main wire (black/white) does not go to the starter. It is linked from the main fuse box to the alternator terminal main mast.

Check the fuse box harness connector below.

Try attaching a wire from alternator to battery and running engine to check if indicator light goes off.

Here is a schematic of the charging system: