During the restore on my 93 D250, I installed a remote PDM (PNDB module) from a Freightliner M2 truck along with a 31 series screw top battery, and new cables in order to be done with the fusible link mess that is so problematic on these trucks.
It turned out to be a very nice upgrade to get rid of those fusible links, and be done with their corrosion and problems for good. Ive had a 31 series battery in the truck for years, with post top adapters. It was a complete mess with all the wires attached to the battery, and the rats nest I had with the fusible links.
Here is what I started with the fusibles on the main engine harness. Years ago, a fusible link blew on me in the dead of winter and started a small fire on the fender harness; and we repaired it "till spring" when it could be fixed properly...I found the rubber junction (broom) all corroded up and now slightly charred due to the small fire from the fusible burning. We removed it in -10 degrees, and this rats nest was born...I have to say, it did work fine for about 13 years...LOL:
Here is the solution, Main PNDB, Freightliner part number A06-72138-012; which is available for around $80; an alternative, if you want a simple battery disconnect switch, A06-72138-013--(you can wire up a low voltage rocker switch in the cab and disconnect the battery remotely, pretty convenient, about $150 for that one).
It includes 3 MIDI fuse connections, and 4 standard ATC blade fuse holders. I do not recommend using the MIDI's that come with it, they are way too heavy for what these trucks run.
Before wiring it up I went thru the entire harness, repaired any damaged wires, and replaced all the dry rotted tape with new vinyl and friction tape, as needed. I also went thru each circuit with a fusible link and identified what it feeds to be able to correctly size the fuses. Here is what the wires feed; in summary, with the fuse sizes I used after identifying the circuits. This is for 1991.6-93 trucks, 90-91.5 are slightly different. Check a wiring schematic for exact components.
40A MIDI; 12ga Pink/Black = Ignition Main Feed
40A MIDI; 12ga Red = Ignition Main Feed
40A MIDI; 12ga Red/White = Exterior Lamps/Headlamp Switch
30A ATC; 12ga Black/Red = Accessories/Power Mirrors
15A ATC; 16ga Pink = Hazard Flasher
100A Remote MIDI; 6ga Black = Alternator Main
30A ATC; 14ga Brown = ASD/Fuel Shutoff Solenoid Relay
40A MIDI; 12ga Red = Starter Relay (paired with 12ga Red/White, no fusible from factory)
20A ATC; 16ga Orange = ECM/A/C Relay
After finding all the wires and separating them, I made a new harness connection in the main engine harness. All connections soldered and covered with heat shrink tubing. Leave plenty of extra wire for locating the PDM:
I also added an extension onto the 6ga alternator feed to allow me to connect a remote MIDI fuse to it.
Here is everything cleaned, taped, and loomed together, and the new location for the PNDB mocked up. I used metal crimp ring terminals at the PNDB connections, soldered with heat shrink. The 4 pin connector in the PNDB is Freightliner part numbers 23-13153-410, FCI/10762803, FCI/10757690 (X2), and FCI/10762802, (this left me with an extra in case I damaged a terminal)...make sure to get yourself a good set of terminal connector crimpers for this, regular butt connector crimping tools will not work. The connector is very easy to put together once you crimp the terminals in, just snap them into the housing. I also put a bit of solder on the terminals for an extra secure connection.
Now to mount the PNDB, I used these rubber studded isolators from a Freightliner, part number 03-35804-000.
Pick a good dry location, and mount the PNDB with the two isolators. I picked the fender well rather than the inside of the fender, in case rain/water got in between the hood and fender. Once the splash shield is installed it will be high and dry. I also recommend spraying the terminals with a battery terminal protective coating. Freightliner makes a paint for this, and I will be coating mine with it here soon.
Here is the 2/0 main feed cable to the battery. I made this using a standard 2/0 x 5/16 terminal end, and a 90 degree battery terminal connector (Freightliner number 23-12776-123). I also connected the grid heater relays and alternator fuse to this terminal. I used a positive and negative cable from a Freightliner, part number JEI/28SP9873R110 (red) and JEI/28SP9851B062 (black), and cut them to the length needed, and crimed on new terminals for the starter, and engine ground. I also made a 2/0 engine to frame ground, and a 6ga battery to body ground off of the extra wire from the alternator circuit.
The new fuses in the PNDB:
Here is everything installed;
Hopefully this gives you a few ideas and helps you get rid of your fusible link problems. If you have any questions about my install feel free to ask.