My truck was down for several months as I slowly chipped away at a high-pressure oil leak problem. In the past week, I finally have it up and running, but a charging problem has popped up and I am at a loss as to what the root cause is.

While the truck was inoperable, I had both batteries disconnected and each one had a trickle charger on it. I always disconnect the ground cable first, then the positive. When I reconnect the batteries, I connect the positive first, then the negative. I did remove the upper alternator so it would be easier to get the turbo out. The batteries were disconnected before the alternator was removed.

As soon as I started the truck the first time, the battery symbol was illuminated on the dash. Torque Pro showed 12.5 volts and declining. With A VOM, I checked the voltage at each battery and also showed 12.5 volts. I then tested each alternator (dual alternators) at the threaded post while the engine was running. The bottom one show 0 volts and the top one showed 12.5 volts. I removed both alternators and went to three different ORielly's (the first two stores didn't have a bottom alternator available) and at all three places the top alternator tested good and the bottom alternator failed.

I purchased a NEW (made in China) alternator, not remanufactured. For a very short moment, Torque Pro showed 13.5 volts, but the battery symbol came back on the dash and I was back to square one. I returned that alternator to the store and they were unable to test it. So I got a refund and purchased a reman alternator from AutoZone. The same problem still exists as I stated above. I've removed the Autozone alternator and will get it checked out at one of the stores near my work tomorrow.

Is there a fuse or relay or something else that may be causing this problem?

 

I wonder what happens when you don't connect the lower alternator at all. Installed and on the serpentine, but no electrical connection. I have dual alternators on my Eseries, but forget how the harness is tied into for the lower alternator. I'd think that if you disconnect the lower alt and the battery light doesn't come on, and you should get ~13.5v with just one alternator. that would isolate the problem to that lower alt harness. Or, if you still had the problem, start checking relays/fuses and that harness.

Sounds like a power wire is grounded and burning out the alternator each time a new one is connected. You're wise to keep moving from one autoparts store to another, lol. Many won't refund electrical parts at all, much less twice.

Do you need the wiring diagram?

 

Yes, I could use a wiring diagram. I will also disconnect the lower alternator and see what kind of output the upper alternator produces. Thank you.

 

You'll need to follow this.

https://www.powerstroke.org/threads/...h-file.903017/

 

Whew, glad Jack responded. I saw your reply and came here to warn you that I don't usually know what I'm talking about - thus the Bonehead username. I'm not sure about anything I said, it just seems logical to me. But, Jack knows. So check out his link. Maybe I wasn't far off.

Here's the wiring diagram I have.

 

I've disconnected the wiring from the bottom alternator and the top one is now producing between 13.9 and 14.1 volts, so it is charging at the moment. I'm going to go back over where I was working on the engine and make sure I didn't leave something disconnected. First suspicion is the ground at the back of the intake manifold on the driver's side.

Thank you for your comments and info thus far. Feel free to keep sharing your thoughts and ideas.

 

Dual alternators = one more thing to screw up. I got dual ACs as well - dang PITA.

 

I'm seeing the voltage go as high as 14.2. Is that ok?

 

Again, I'm Bonehead, and know even less than nothing about electronics, but the way it's burning out the lower alternator sounds more like a hot wire issue than a ground wire issue, I guess unless a ground wire is connected to a hot wire.

 

Oops, you squeezed your last reply in between two of mine. I wasn't answering you. I don't know if how high is too high. I'm thinking it goes higher when you have undercharged batteries. Hopefully one of the smart guys answers.

 

Problem solved, time to eat some crow. I overlooked reconnecting one of the red cables that connect to the positive side of the passenger side battery. It had fallen down and was easily overlooked. Now, both alternators are putting out 13.8 volts.

Thanks for all the suggestions and info you have shared!!

 

Hah, takes more than that to take my Bonehead crown. When all I do wrong is forget to connect a wire, that's a good day. Glad to see you got it fixed..