General Alternator question.

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Jul 19, 2006 | 06:30 PM

DOUG5G

Thread Starter

Mountain Pass

Joined: Jun 2003

Posts: 208

Likes: 3

From: Norfolk VA

General Alternator question.

My neighbors Ford reads 14V while at idle. If we rev the engine up to around 2000 RPM the voltage drops to 12.5 and the battery light comes on. The belt is tight and the alternator is about 4 months old. Does this sound like a belt issue or can the alternator be bad? It has an the spring automatic tensioner so how can I prove what is wrong?

Now the bad news....This alternator is on a 1997 Expedition. I posted in that forum but that one is not as good as this one in getting good answers.

Thanks for the help
Doug

Jul 19, 2006 | 08:05 PM

99f350sd

Lead Driver

Joined: May 2003

Posts: 9,303

Likes: 48

From: Lyndonville, Vermont

Usually that happens when the brushes are wore or the armature is egg shaped. My bet on a 97 is that it needs replacing..

Dick

Jul 19, 2006 | 10:16 PM

bear2x2

Senior User

Joined: Jul 2004

Posts: 184

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Make sure all connections are good and tight first.

Jul 20, 2006 | 07:47 AM

VanGo

Elder User

Joined: Apr 2005

Posts: 882

Likes: 0

From: Wichita

You can get it tested at a parts store.
I was thinking bad voltage regulator. I can't imagine an alternator wearing too much that quickly. Anything is possible.