'03 4.0 -- low voltage on alternator "A" terminal - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 08-03-2015
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'03 4.0 -- low voltage on alternator "A" terminal

Hi Guys:

'03 4.0L w/228,000 miles that I haven't had registered in a couple years (wasn't charging when parked) that I'm in the process of resurrecting.

After putting in a new battery, alternator and belt, the dash low voltage light was still coming on below 2500rpm.

Checked the terminals today -- 12.3v @ battery, 12.3v @ B+ terminal, 0.4v @ A terminal (Yellow/White wire) which I believe is the exciter voltage...ah hah! From what I found online that should be at battery voltage.

But the yellow/white wire disappears into split loom...and all my googling and reading the owners manual has left me with no clue where to look for a fusible link (that I think it has) or maybe which fuse if fused. It may be that I just don't know the right term to search for!

So, before I start cutting open the wiring harness at the alternator and working back to trace the yellow/white wire...any pointers where to look?
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Old 08-03-2015
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In my diagram for a 2003 4.0l, it does show a fusible link for A (Yellow/White wire).
It also shows that it connects to 2 other fusible links used by B+

-----fusible link-\-----------fusible link----- (Yellow/White wire)------A
-----fusible link--\----B+
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File Type: pdf 2003 charging.pdf (27.1 KB, 42 views)
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Old 08-04-2015
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Thanks!

At least I know for sure how many of what I'm looking for...just not exactly where to find them yet.
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Old 08-05-2015
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Follow up:

Found the "fusible links" by the battery...wires were clearly marked "fusible link" which made it easy once I started looking.

Removed battery to have room to work.

Soon as I cut open the shrink tube on the battery side of the assembly, the battery side of the fusible link that feeds the exciter fell off -- completely corroded.

The crimp for the other two fusible links was solid.

Stripped the end, checked for continuity, used a piece of bell wire which I twisted to hold the stripped end of the fusible link to the outside of the crimp, soldered it, wrapped in tape, and we were good to go.

Truck passed emissions, so Friday I'll get permanent plates...but I'll have to wait till I buy new tires before I put any heavy loads in the bed. Fair amount of dry rot on them.
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Old 08-05-2015
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Thanks for the follow up.

And good work on the testing and then the fixing, very smart logical thinking

Last edited by RonD; 08-05-2015 at 10:22 PM.
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