Here's the backstory. Please note I am electrickity disadvantaged ... so I hope I describe the situation correctly.

Before New Year's, my battery dash light started coming on intermittently. After a day or two, the light came on steady and stayed on. Truck still started strong and ran fine. Batteries tested fine (only 2.5 years old).

Alternator specialty shop swapped out the alternator but dash battery light still stayed on (they actually swapped 3 of them in and out thinking maybe bad regulators inside the new alternators). All three replacement alternators charged strong (14.5v'ish) ... problem is the dash light remained on after new alternators were installed. Shop told me maybe it needed to charge up and settle down and said to come back in the new year if battery light remained on ... it has.

Came back yesterday (3 weeks after new alternator installation completed). Confirmed batteries good, new alternator charging as it should, all fuses are good (visually inspected and also tester verified) at both the under dash central junction box and the under hood battery junction fuse box (specifically the #5 fuse - 5 amp mini for generator).

There is power leaving the #5 spot but no power received at the generator through the orange/light blue wire which IIRC feeds the regulator/battery dash light circuit thingy. They jerry-rigged a separate power line to the alternator from the battery (in place of the orange & light blue wire I think) and the dash light went out when engine running.

The techs concluded the orange/light blue wire must be broken in the loom somewhere between the alternator and battery junction box. A visual inspection of the loom (as much as you can see of it) did not reveal any obvious rub points or breaks.

As opposed to spending hours dismantling and hunting down where the wire might be broken in the wire loom, they are proposing to run a new, separate wire from the battery or junction box to replace the old, non-functioning wire. They don't believe it is a short because they said it would have blown the fuse which it did/does not.

Sorry for the long run up. Does their diagnosis sound right and is their solution of running a new wire sound like a reasonable one? Any other thoughts or options? Thanks.

 

The question I have is, "Will running the new wire result in the the warning light not working as originally intended?"

 

That's a good question and I asked it of the shop tech. He said it would be the same as before the original alternator failed. When they ran a new temporary wire, the dash battery light went out as it should with the truck running.

He said another alternative was he could make it so the dash battery light stays off permanently. However, it would never come on if/when this alternator goes so he advised that is really not a good solution.

 

So I wanted to close the loop on my problem. It appears the wire to the alternator was bad. The tech thought it was likely broken completely or corroded completely. He did not try to find the break as he said it would involve a bunch of unknown hours tracing the orange/blue wire back through the loom.

Instead, he ran a new wire from the under hood battery junction fuse box to the alternator. He ran it in its own, separate (small) loom. Now, the dash battery light comes on with KOEO as it should, and goes off once the truck is running ... as it should. Problem fixed.

Since they replaced the alternator initially, the real question is ... was the original alternator OK and just the wire needed replacing? I'll never know. I should have insisted they test the alternator first before allowing them to replace it. Live and learn. Hopefully this post will help the next person.

 

Thanks for "finishing up he paperwork".

 

::: have same problem which wire did he hook it to on the fuse box under hood

 

a bad or poor connection can destroy an alternator...
same with a bad ground connection for the alternator.

going from low charge to high charge to low charge every few minutes.. makes lots of internal heat.

 

One end of the Orange/Light Blue wire will go to the "A" terminal on the generator(s).

Depending on what engine/generator configuration the OR/LB wire will go to different fuses. I think for diesel single generator it is 10 amp fuse #6. For dual generators it may be 5 amp fuse #7 for primary generator and 5 amp fuse #5 for secondary generator. Gas engines use a fusible link to power OR/LB wire which connects to generator terminal A.

 

ty jetty I try that today. Everything else is new

 

ptr34, did it work? There's another fella dealing with the same issue in another thread and it would be good if you could comment and close this loop.

 

My wire at the battery was broken and u couldnt tell till I put the meter on it. Its on passengers side where all the wires go together. So I didnt have power at alternator

 

OK. So different problem ... different solution. Thanks for finishing your story.