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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.
 

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Very nice!!! I have been dreading the day I have fusible link issues and now this is a great way to fix it for good. What are the specs on the battery you installed?:yourock:
 

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Discussion Starter #3
Very nice!!! I have been dreading the day I have fusible link issues and now this is a great way to fix it for good. What are the specs on the battery you installed?:yourock:
Thanks, battery is a 31 series, 925 amps at 0*, 1110 amps at 32*; can be had at any Freightliner dealer, part number ABP/31S925; was $60 on sale.
 

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couple of questions, first, did you get the block straight from Freightliner? haven't found a decent source online for one.

also, you list 4 midi fuses in addition to the remote midi fuse for the alternator but the block only has 3. where does the 4th go?

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
 

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Discussion Starter #9
couple of questions, first, did you get the block straight from Freightliner? haven't found a decent source online for one.

also, you list 4 midi fuses in addition to the remote midi fuse for the alternator but the block only has 3. where does the 4th go?

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
Yes, all came straight from a Freightliner dealer. It is proprietary stuff, so I highly doubt its available online.

The 4th midi in my list is paired on the same post with the headlamps/exterior lamps circuit (red/white). It is for the starter relay, and had no fusible link from the factory.
 

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never mind, i see it now, you have it paired with 12ga red/white. guess i should read better...
 

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very clean install. Awesome!
 

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This write-up adds a lot of value to this forum. Thank you for taking the time to do this as it has helped me out and I'm sure will benefit many others in the future. Forum god, will you please make this a sticky? :)
 

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Discussion Starter #13
This write-up adds a lot of value to this forum. Thank you for taking the time to do this as it has helped me out and I'm sure will benefit many others in the future. Forum god, will you please make this a sticky? :)
You are welcome. Hopefully this will be a good long term solution for the electrical issues common on these trucks. Feel free to ask any questions, I will help any way I can.

I am going to add the part number for the glow plug relays; several have asked me where to get them:

They are available online from many sites, under part number 120-105711, just google search it; they are made by Westinghouse, White-Rodgers, and several other manufacturers. Make sure you use that part number, as it has an isolated ground circuit in it.

On a side note, I accidentally tested the PNDB the other day, I was checking the vacuum sensor to see if it worked, accidentally grounded the sensor power wire, and boom, blew the 40 amp midi instantly...engine shut off, dash went dead, good to know it all works. :laugh:
 

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My truck is 93 but I can't seem to find the orange wire for the ecm/ac relay or the red wire for either that starter relay or ignition main feed.
 

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Book marking this page for the near future! Awesome job and nice details! Thanks! Best Regards, TK
 

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Discussion Starter #16
My truck is 93 but I can't seem to find the orange wire for the ecm/ac relay or the red wire for either that starter relay or ignition main feed.
You will see the orange and red wire coming directly out of each relay; you can follow them from there.

The red ignition feed wire will be in the original "broom" junction on the fender.

If you still cant find them send me some pics of your wiring setup and I will check it out.
 

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Alright thank you I will take a look at it tomorrow evening and let you know what I come up with. Also I was wondering on the side closest to the battery I have two small red wires that were wired into one white fusible link and also a bigger red wire and black wire. The black is for the alternator and the red to the battery but what are the two small wires for?
 

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Discussion Starter #18
Alright thank you I will take a look at it tomorrow evening and let you know what I come up with. Also I was wondering on the side closest to the battery I have two small red wires that were wired into one white fusible link and also a bigger red wire and black wire. The black is for the alternator and the red to the battery but what are the two small wires for?
Send me some pictures of what you are dealing with, and I will have a look.
 
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