Hello, all, I need to first apologize for just throwing this out here; I had very limited luck in searching about my problem because I'm not sure how to best word the searches. Second, I need to apologize because I am posting this to three forums for Fords because I'm not sure which will have the most active users.

On a 2010 F350 Diesel I'm helping a guy with: batteries found dead one day. One tested bad. Guy jump started truck (with 12V) and drove to store to get batteries and then changed them. After changing batteries, however, the truck will not start. This is the point I got called in.

The batteries are connected correctly (parallel). The ground wires to each battery are connected to the chassis and verified with a digital multimeter set for continuity checking. What I call the PDM (power distribution module), fuse block, under the hood supplies several circuits in the cab. The PDM has voltage from the batteries, verified with the meter.

This is where it gets weird: the 12V outlet at the dash near the steering wheel has power, the passenger-side electric seat works. However, turning the key to the run or start position gets no response, the same as the horn, hazard flashers, brake lights, driver's seat, and instrument cluster. Just dead. I removed the fuse from the passenger-side electric seat and switched it with the one for the driver's side. The passenger-side seat continues to move/function, and the driver's seat continues to not work. I found 12V at the fuse connector for the driver's side seat...but it still doesn't work.

This confuses me; some circuits from the PDM in the engine compartment work, and some do not. I'm at the point where I think it can only be a ground wire which exists under the dash and only is connected to some circuits, meaning power from the batteries for other in-cabin devices can flow across some other ground wire exclusively for them.

I'd love to have some input, please. Also, if someone can tell me where a community ground wire for the listed affected circuits is under the dash I'd appreciate it so I can check it.

Thank you.

--HC

 

was the battery hooked up backwards?

it sounds like some fusible links were blown. I would start with either a power distribution or starting system diagram and trace back the circuits that do not power up. the power distribution shows 7 pages of diagrams.

if nothing on powers up at key on; check the ignition switch circuit.

 

Thank you for your reply.

I understand words "fusible" and "links", but I'm not sure what a "fusible link" is. I understand a fuse, but if a "fusible link" is not a fuse, then I'm sorry, I don't know what that is. I cannot say if the battery was hooked up backwards or not, but I can say that the guy who did this has done some dirt track racing and has a small shop where he tinkers on some cars; I would expect he wouldn't do that...but mistakes happen.

I have no diagrams for the vehicle and the owner only has the Owner's Manual. What you suggest, that it's the ignition switch circuit makes sense; if some circuits are getting power from the PDM (or PDC) under the hood, and some do not, it's entirely possible that the circuits which carry power to the switch and then on to the other circuits are not getting energized.

I'd still like to find that there's a cab to chassis ground that's broken which only supplies ground for some of the circuits, explaining why the passenger seat or the power port work, but not a bunch of other stuff.

--HC

 

I called the guy after the initial responses across my posts to tell him I'd not forgotten him. He told me he just got it fixed. Another guy he knew came to look at it and knew what was going on.

On the passenger-side battery, he tells me, there is supposed to be 3 wires to the positive terminal. However, there were only 2. The owner who changed the batteries apparently dropped one of the wires and didn't remember that it had been there. The wire is, reportedly, very short, and was not visible once it had fallen down. Upon connecting this 3rd wire, everything works.

Now, WTF?! Why does the passenger-side power seat work but not the driver's-side seat? Both fused through the same PDC supplied, apparently, by one cable from the driver's-side battery. I don't know. But I do know the owner tells me that the truck works now because one other cable to the passenger-side battery is connected. Engineers.

--HC