Help!! Alternator shorted out, new alternator only at 12.3 volts - Jeep Wrangler Forum
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Old 11-07-2015, 02:11 PM
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Help!! Alternator shorted out, new alternator only at 12.3 volts

The steel box that isolates my air filter from the rest of the engine compartment came into contact with the post on the alternator of my 2005 LJR and shorted out the alternator. I replaced the alternator with a new one, but now a multimeter at the battery only reads 12.3 volts with the engine running. I know the new alternator is fine, but what the heck do I need to check or replace next?

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Old 11-07-2015, 06:21 PM   #2
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Unfortunately on the TJ the voltage regulator that controls the charging is part of the main computer called the PCM power train control module

Sucks as pretty expensive

First check the wiring for damage

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Old 11-08-2015, 07:51 AM   #3
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Originally Posted by Jackdanielsdad View Post
The steel box that isolates my air filter from the rest of the engine compartment came into contact with the post on the alternator of my 2005 LJR and shorted out the alternator. I replaced the alternator with a new one, but now a multimeter at the battery only reads 12.3 volts with the engine running. I know the new alternator is fine, but what the heck do I need to check or replace next?
Try this.
With the Jeep running ....... lights on and hvac fan running ....... your test point is at the back of the alternator ........ multimeter positive to the B+ pole on the alternator, multimeter negative to ground.
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Old 11-08-2015, 11:14 AM
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Ok so I found the wire that fried yesterday. It was the short piece of wire that comes out of the harness right by the battery, and runs into the fuse and relay panel. It runs to a plate with 2 posts on it and then right back out to the battery. When I jumpered alternator post straight to the battery, it charged correctly and read 14.5 volts. So it appears the regulator was not damaged. Now my question is what purpose that 2 terminal plate in the fuse box serves, and can I just run a new charge cable straight to that plate? Or should I patch one in where the last one fried and put an inline fuse in while I'm at it?
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Old 11-08-2015, 11:30 AM   #5
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That two terminal plate is what provides +12v to the Power Distribution Center, and serves as a 'junction' to connect the alternator to the battery.

The charge cable between the alternator and PDC has a fusible link in it so don't replace it with just a straight piece of wire. It's a 6 gauge wire which has a 10 gauge wire crimped into the middle of it which serves as the fusible link.

You can see it at the top right in the below diagram.

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Old 11-08-2015, 11:43 AM   #6
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That two terminal plate is what provides +12v to the Power Distribution Center, and serves as a 'junction' to connect the alternator to the battery.

The charge cable between the alternator and PDC has a fusible link in it so don't replace it with just a straight piece of wire. It's a 6 gauge wire which has a 10 gauge wire crimped into the middle of it which serves as the fusible link.

You can see it at the top right in the below diagram.

You can buy a new fusible link at a NAPA store, probably any autoparts store, but I've bought one at NAPA before.

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