Hi, guys. My 2004 6.0 with dual alternators doesn't get a lot of miles so problems don't crop up often. But yesterday my battery light came on going to a relatives house way up on a steep mountain in NC. Last year I had my FICM rebuilt and put in 2 new AGM batts at the same time. After that it roared to life regardless of weather.
I tried disconnecting the alts one at a time and found that disconnecting the hot lead on the top alt put the light out so I thought I could at least limp home today. I figured that the bottom was charging and that would work. I checked the batts today, however, with a meter and found no charge. 11.5 with engine running. I packed up to get home in daylight and went about 4 miles down the mountain. On the flat the truck only went to second gear and would not up shift any further. I turned around to get back to safety and on the way back up I got the ABS light and then all the gauges went to zero and I couldn't put the window back up. Total electrical shutdown but it kept running. Last night I ordered a new upper alt thinking that was my issue. That's on the way but I want some opinions on what to do next. Is it possible that both alts are bad and I should replace the lower, also? I'm wondering if an alt fails can it take out the other 'good' one? I'm also hoping that in that short drive I didn't screw up the FICM. With the tranny not shifting my first thought was that second gear is actuated hydraulically and 3-4-5 are done electronically, hence no shifts? I'm getting this rig ready for a 2k run to Arizona on New Years and I want this done right.
I've owned this since 2006 and the alts are original AFAIK with 160k on the clock. Thanks in advance for any hints and hope you had a great turkey day.

 

11.5 is purdy low, take the top off and get it load tested , if it comes back good do the same for the lower Alt.

 

You could very well have both alternators be bad. The top 140amp could of quit first and the lower 110amp may of now quit.
With your miles and upcoming trip I would replace them both and be done with it. Also inspect both tensioners and replace the belts.
Also charge the batteries before your first restart with the new alternators.

 

Thanks for responding, guys.
87, it never occurred to me that one unit could have died much earlier. I thought the system needed 2 good alts to function but that really opened my eyes. I suppose I could have driven for a couple years just running on one. I have to get back to the truck ( 50 miles away) and pull both units off. Even if one checks good with the years and miles I will put 2 new ones on along with belts. Have you guys ever heard if there's premium belts out there, like the silicone hoses? I never thought of the tensioners but a few posts mentioned the pulleys spinning off due to bad tensioners. Again, crossing my fingers it didn't do any other damage to electronics, etc.

 

IF both alt are bad I'd think about doing one big alt and upgrade the grounds and positive leads to the batteries. It would be cheaper in the long run and more efficient. Have you done any of Jacks mods to your truck?

 

I know in our fleet of 2008's we often have both alts go bad. I theorize that one goes bad and the truck runs on one for who knows how long.

 

I hope you didn't dust your FICM with the low voltage. Keep your fingers crossed.

 

I had the FICM rebuilt last year when I pushed my batts too far. It was like a new truck after that. I don't know how much abuse they take but I was at the point that all the electrics shut down. I had to run it that way for only about 7-8 minutes but that's probably light years in electrical terms. When I shut it down the batts were at 10.8 v.
I mentioned earlier that I didn't think the truck could have an alt go out without throwing you a light because I didn't know how the system was wired. If it can then who knows how long I could have had one bad unit.
I haven't seen Jack's info. Is that the video about running larger cables?
Just want to tell everybody that I'm going on a cruise Wednesday for 2 weeks and don't think I'll accomplish anything on the rig until I'm back. I don't want you to think I'm in radio silence. Keep your ideas coming, I'll check the internet every chance I get. I have an upper alt already coming so I'll probably stick with the dual setup and order a new lower. I did look at DC Power and their kick *** units but the web says everything is out of stock. Thanks again, guys, and enjoy the holidays. Ed

 

And check the reports on there service... couldn't pay me to take one of their units, although Ed is trying his darned'est!

 

Check at FICMRepair they seem to have stock. I am ordering a 185 amp from there tonight once I determine the connector used.

 

If you use coupon code SAVE15 you can get the leece-neville 230 amp unit for $297 this week. Part of cyber monday sale xdp is having.

Leece-Neville 230 Amp High Output Alternator AVI160T2002-2

 

Just got back in town and started pulling the truck apart yesterday. I decided to go with 2 stock replacements to expedite the repair. I probably made a few stupid moves doing this for the first time but I now have the whole shroud out and the fan blades unbolted along with unbolting the rad and pulling it forward. Seems like a lot of work to replace 2 alts and belts. I'll get back at it tomorrow but I discovered that the hot lead with the fusible links on the lower unit has melted apart. It's the main wire, guessing about a 6 ga? The fusible links look fine. I'll have to make that repair first because it looks like that piece is part of a much larger harness and not easily replaceable. I know some guys recommend running a larger hot wire from the alts to the batteries but doesn't that circumvent the idea of fusible links?
Have any of you replaced both units and belts? I've seen the single alt job done and it looks like a breeze by comparison. Hope to be running by tomorrow.
Hey, Dr. Huxtable...just noticed your Spartanburg home. Going shopping there today. I'm in Tryon, NC. About 25 miles away.
Thanks, guys, for all the input.

 

When you run a larger cable because of a higher output alternator members usually install a fuse rather then splicing in a fusible link. A fusible link is just a smaller copper wire then the ends to control where the interruption will occur along with insulation that won't continue to burn. I'm surprised that it's the larger end cable that burned up from excessive current then the fusible link(s).

A burned fuse link/cable is pretty rare, but I'm glad this bad for you occurrence is reported as it can be difficult to get some people to installed the fuses due to the "I've never seen that happen" mentality.

 

As Jack stated, never run any circuit no matter how small or large without over current protection. Other wise you could burn the whole truck down.

 

Did you check to see if you had EXCITER voltage at the alternator connector. I'm thinking that one went bad and maybe shorted the exciter voltage to both. There is no fuse or relay for the exciter voltage but according to my wiring diagrams there is a dark blue 20 gauge fusible link that provides power to the exciter field.


Ed