Hello! I have a new to me 2003 7.3 EB. The van is cherry but had been sitting for a while when I purchased it. I bought the van, drove home 14 hours (slept overnight as well) with no issues (ie...van started the next day).
The only thing I noticed on that drive was when I put the key into the ignition and then did the requisite half-turn for the diesel, the van gauges and lights would do their normal thing (ie...lights light up and gauges move) and then I would hear a sort of click and they would do it again. The second time they would act normally and the van started fine.
Fast forward a few weeks and the van has been dying if I do not keep it on a charger (haven't been driving it at all). I had the battery under the hood load tested (Interstate AGM 850 CCA) and it came back good. The battery on the frame rail was toast (led acid. Completely dry. 7 volts), and the house battery is toast as well.
I replaced the battery on the frame rail with an exact match to the one under the hood (Interstate AGM 850CCA), cleaned all of the connections (lots of corrosion) and reinstalled everything. I am getting 13V at the terminals.
Once I was finished, I put the key in the ignition and got a nice "ding ding ding" sound and when I went to my half turn the dash lights and gauges went haywire then all electric died. Now I have no electric anywhere in the cab (no locks, no dome lights etc...).
When I did the aforementioned start, I had the isolator CLOSED so that (at least in my head) I would be only using the starting batteries to start the truck.
I re-attached the house battery and opened the isolator and tried again....nothing. But...all of the house items work (ie...fridge and sink pump turn on etc...). I know the house battery is bad (already have a replacement on the way) but there is enough juice to turn on the fridge etc.
I un-did all of my work to make sure 100000% the cables were going to the correct terminals (they were correct).
On my van I have a house battery (4D) ---> frame rail battery (AGM 850CCA ---> and a terminal next to the frame rail battery where the POSITIVE cable from the house battery, the frame rail battery and the engine battery meet.
I cleaned the hell out of that terminal and even removed the house battery positive cable to see if perhaps that was the issue. No luck.
The weird part is after removing the house battery POSITIVE cable from the mid-ship terminal, I was able to put the key in and get a weak "ding ding ding" but this time I turned on my fog lights (no ignition turn at all) and they turned on very weakly, but after 30 seconds the van went completely dead again.
The internet is telling me it is potentially a bad ground somewhere? I was thinking fuse? PCM? Relays? Maybe a rodent chewed a wire over the course of the last few weeks when she was parked? Not even the key FOB responds. 100% dead.
Thank you in advance if anyone can help!