Melted Alternator Cable! - Diesel Forum

cre8ive · 09-24-2007, 11:45 PM

<span style='font-family: Comic Sans MS'><span style='font-size: 11pt'>So I was doin' a mileage check this weekend and when the first tank ran empty, I switched over to the other tank.....Bad Move. Learned my leasson there!! It didn't catch and the truck died! Got off the freeway and ran the batteries down trying to start it. Lucky I had friends along with their diesels and jumper cables. We used 2 sets of cables between the trucks and finally got it started. After a while, I noticed the battery guage slowly but steadily dropping voltage. I was 1 hour from home and decided to make a run for it. Made it home, barely. Tonight, the batteries were dead. I inspected the alternator, and found the large wire on the back of it melted off! Jumped the truck and measured 34 vdc on the alternator side where the 8 guage wire should be connected. The others on the small 3 pin connector were I think 13 vdc, 12.4 vdc, and 12.4 vdc.
Should I replace the alternator, have it rebuilt, or is it something else? Not really sure what the output should be with no load on it.
Hope someone can help.

thanks,
kevin</span></span>

typefour · 09-25-2007, 12:54 AM

It should be 13 or so, the dead batteries finished off the diodes in your alt, you need a reman, take it to a GOOD autoelectric shop and get all the upgrades put in. Heavier diodes, output terminal upgrade kit, those are the 2 I can remember from the electric shop days. There is more but the memory is first to go, right?

arthurgoboom · 09-25-2007, 12:59 AM

Sounds like you have burnt out the diodes, probably from trying to recharge the dead batteries. There is a warning when you buy alternators to replace the ones on these trucks that you can damage the alternator if running the truck with less than fully charged batteries. It's meant to maintain the full charge, not recharge them when drained.

If you have an auto electric rebuilder in your area, You could have your alternator rebuilt. It'll most likely be cheaper, and it should perform like new. I prefer my local electric rebuilder over auto parts stores.

Edit: ahh, posting at the same time lol

Aubrey · 09-25-2007, 02:02 AM

BTW, there is a 130A alternator with internal regulator that fits these trucks. Save your pulley. The 130A alternator has a bigger front bearing and much better charge at idle. You have to get the earlier 130A frame type. Most advertised 130A alternators are for later serpentine installations but any autoelectric place will have the earlier frame model that bolts right onto our engines. The wiring change is minimal for the internal regulator.