FYI Alternator Rectifier

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Aug 27, 2004 | 03:32 AM

Muffinman

Thread Starter

Laughing Gas

Joined: Jun 2004

Posts: 1,240

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From: Dallas, Texas

FYI Alternator Rectifier

Just went through a 2 day trouble shot with a battery that was going dead over night. It had a new battery and voltage checked out fine. I checked it for a short by hooking up a 12volt test light on the negative side and had no drain. Checked voltage output of alternator while running and it checked fine. Could not find any shorts no where.

The problem was a faulty retifier was letting the battery bleed back voltage over night and would drain it. Went to a junk yard and picked the best factory one I could find "$25.00" and pulled all the parts off it cause it had one of those cheese looking flex fans. Fixed the problem right up and got a 85 amp rectifier to boot.

Aug 27, 2004 | 08:01 PM

lasher

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Joined: Feb 2004

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that happens when someone jumps starts with cables reverse and it blows the diode.
FYI

Aug 27, 2004 | 08:14 PM

Muffinman

Thread Starter

Laughing Gas

Joined: Jun 2004

Posts: 1,240

Likes: 3

From: Dallas, Texas

problem was it never has been jumped. I always charge the battery outside the engine. It was just it's time to go out.

Aug 28, 2004 | 03:37 PM

SgtJoe

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Joined: May 2004

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From: Vandenberg Air Force Base

Heat can be a factor too. Diodes do not like heat. If you think the rectifier bridge is at fault, you can disconnect the alternator overnight. If the battery doesn't die, then you have bad diodes. I've seen this quite a bit, especially on heavy equipment.

Good troubleshooting Muffinman, good to see that someone still fixes versus replaces.

Aug 28, 2004 | 03:54 PM

Muffinman

Thread Starter

Laughing Gas

Joined: Jun 2004

Posts: 1,240

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From: Dallas, Texas

Quote:

Originally Posted by SgtJoe

That is how I found it. I unpluged the harness and let it set over night and it stayed charged. Also when I took all the parts off the Junk yard one I applied CPU thermo paste on it. The reason I like to keep factory parts cause the rebuilds are cheap junk "Flex Fan" compared too a Ducted backing plate fan the factory makes.