I've been working on this truck for a month now (2005 F350 6.0) and finally got her out on the road this morning, only to have it die about 45 mins into my delivery route. I actually drove it to work 30 mins, it sat for an hour while I loaded, started right back up, then again at the gas station, and finally drove 45 mins before dying. While I was doing the engine work, I accidentally unhooked the alternator without unhook in the batteries, and I leaned over the alternator and the power wire touched the casing of the alt, sparked, and the positive battery lead on the passenger side arced to the AC line and actually smoked a little. So this morning all the lights were going dim but I kept going. Finally the radio started cutting out, lights were so dim I could barely see, so I headed home and it died before I got there. I had the voltage regulator on the alternator replaced by a shop today, and the batteries still had a little over 12 volts but when I turn the key, I get flickering lights and relays, and the voltage drops to around 7.5 koeo. It did this same thing this morning before the voltage regulator was replaced. I'm really hoping I didn't fry my PCM or something. I don't know much about batteries, but I have been charging them and cranking on them a lot during this low oil pressure fiasco. Does it sound like my batteries have just gone bad? Or should I be looking for a loose ground somewhere? I apologize for the long post, I am just not very knowledgeable with batteries and voltage. Im really just looking for a second opinion. Thank you

 

Most likely when you shorted the alternator cable you blew the fusible links between the alternator terminal and the battery, so there is no connection between the alternator and batteries to recharge them.

That might be the good news. Driving and running down the batteries as you did puts the FICM in high risk mode. FICMs don't take kindly to below 9v. And the overall workload that the batteries have been going through may have injured them as well.

The shop should have checked a few things before replacing the v regulator unless you were specfic in having them do that. But the regulator may have been fine.

To start with you need each battery fully recharged then tested to see if they both are good or need to be replaced. Most auto parts stores can do the testing.

Once you have a good set of fully charged batteries the charging cables need to be looked at. Since you had a shop do a v reg, I'm not sure how you are in doing electrical work. The standard shop procedure would be to replace the harness for the alternator/glow plug module/ battery connection if the fusible links are blown, although a real good shop would just splice in new 12ga fusible links. A secondary method would be to cut the fusible links and positive cable at the alternator and use a parallel cable with a fuse just like installing a high output alternator. So there are three ways of dealing with this.

After the batteries and charging circuit are in good condition, then you'll need to see if the FICM got hurt by the low voltage. But once headlights start to go dim, this is a motor that needs to be shut down pronto and repaired.

 

A dead short on a battery that isn't up to par is like running with stitches on your knee. Could just open up the wound. If you had a battery that was on the way out, the dead short could've put the nail in the coffin for it.

When running into electrical issues always start with the basics. Batteries, positive & negative connections, fuses, etc. Doubt that your dead short harmed anything other than your batteries.

Get them batteries checked asap if your fuses & wiring looks good!

 

No concern about letting the smoke out of the fusible links, eh?

 

I type too slow! Had no idea there was a fusible link inline with the alternator to battery wire. Learn something new everyday. Listen to Jack! I haven't been here very long but know he's very very knowledgeable on every electrical component on the 6.0!

 

Yeah there's a black protective sheath on the passenger battery + wire where it bends downward right by the AC lines, that's where it arced. Through the sheath and all, and definite smoke. This is my first diesel truck and I've got a lot if help from this site. I've got the batteries charging overnight, will go from there. Is the fuseable link visible if I inspect the wire?

 

Naaa, just learning like everyone else.

 

The easiest way to check the fusible links or cable is check for 12v+ voltage engine off between the alternator positive output terminal and the alternator case or pass batt neg terminal. If it's 12+, the cable is good.

Need to go to my Dell to get pictures.

 

The interior light, dash lights flicker with koeo and quickly fade to nothing, but if I leave the key off, the interior light stays nice and bright, and headlights are even brighter. Could I have fried anything to do with the actual ignition? The radio is hard wired to stay on with the truck off (it came like that and I haven't fixed it) and it has plenty of power until I turn that key. I had started to suspect the ignition switch myself.

 

Not even the headlights are as much of a draw as the motor electronics. The next highest are the glow plugs and the most the starter.

You really need to check the batteries first because if the two reservoirs of electrons aren't of good capacity, you can't make good calls on what's wrong.

My speculation from this side of an oblique screen from the description is the batteries are low on capacity. That's not necessarily volts, but the CA or CCA reservoir they have. Charging may or may not replenish that based on the condition of the lead plates inside.

I've got a 12 year old battery in my lawn tractor at home that charges and shows 12v. It has 200 CCA of its 500 CCA rating, but that little guy only needs headlights worth of current to start right up. It wouldn't get my wife's car to turn over if I tried.

 

At that splice in the picture above it shows the five fusible links. Two 12ga go to the glow plug module (GPCM), the minor diameter 20ga goes to the sense wire terminal at the back of the alternator, and two 12ga splice back into the 6ga cable that runs to the alternator power stud ending the the terminal that got wild.

If the fusible links are shown to be severed by checking voltage at the alternator terminal when the motor is not running, you can install a 6ga wire between the alternator to the battery in place of the factory cable. But in short order you do need to get it fused, and well, you already kind of know why. The easiest fusing is a Blue Sea mount with a block fuse that installs onto it.

 

I went back to the truck with fully charged batteries, and got it started, and checked with my voltmeter positive lead on the red wire connected to the alternator, negative on the battery negative post and got next to nothing. I believe it had .2 volts. I was on the side of the road and watching several things, but I did check for voltage several times and never got anything. So my alternator is done, right? I need to replace it first and foremost? Or could anything else cause that? Thanks again for the help guys

 

Well, TooManyToys was 100% correct. I'm posting a pic below. Where did you get that Blue Sea mount with the fuse? I definitely want to get one put on. I melted 2 of the wires. I'm not sure where both go, but hopefully I can find out. I have the truck home now so I can work on it.

 

Replace the wire, alternator isn't necessarily done, you touched the positive battery cable to the negative grounded case.... just like touching anything else that is grounded to the frame or body and block.

 

Yeah I just had the alt tested and it's fine. I just need to find where to buy those fuse blocks. I found them on the Blue Sea website, but I'd like to buy them in a store if possible. I also don't know if I need to buy the "double" one they have since I melted 2 wires or no.