Wiring Harness Question

[rmesgt]

Hello all... I recently purchased a replacement FRONT wiring harness. It very closely matches the existing wiring harness, but the new harness has several different wire numbers compared to the existing. Additionally, the new wiring harness has connectors that the existing one does not have. It seems the new wiring harness is designed for a vehicle with a generator and my truck has an alternator. The new wiring harness has a heavy wire that runs from where my alternator is, across the engine side firewall, to a plug that contains two large pins. It appears that this plug is supposed to go into something (such as a voltage regulator) that would be mounted to the drivers side of the side firewall.

While researching this bit of confusion, I came across an Alternator/Generator conversion kit (NSN: 2920-00-000-008. This kit seems to have the stuff (and instructions) necessary to modify the replacement wiring harness to fit an alternator style truck. What do you all think? Have any of you run into this? Please let me know...

Peace in Christ...
Leo

 

[Barrman]

That generator to alternator kit works great. I have used it on several trucks. You also will find since your front harness is for a generator truck that it probably doesn’t have the front axle engaged light plug either. At least that has been my experience. Everything else will be close or just right.

 

[rmesgt]

That generator to alternator kit works great. I have used it on several trucks. You also will find since your front harness is for a generator truck that it probably doesn’t have the front axle engaged light plug either. At least that has been my experience. Everything else will be close or just right.

Thank you for your reply! I am just now getting to the instrument cluster, so the front axel engagement light problem will probably rear it's ugly head some time this week. Today I have to figure out how to connect the flasher unit.

 

[Barrman]

Do you have the solid state blinker wiring or the old mechanical Spartan unit wiring for blinkers in your new harness? As long as you have your old 3 pin plug for the box and the harness from your blinker arm, it can be made to work. I did that on my M715 which is exactly the same as the M35A2 except for wire length.

 

[rmesgt]

Do you have the solid state blinker wiring or the old mechanical Spartan unit wiring for blinkers in your new harness? As long as you have your old 3 pin plug for the box and the harness from your blinker arm, it can be made to work. I did that on my M715 which is exactly the same as the M35A2 except for wire length.

Barman, thank you so much for responding. The flashing unit on my truck is bolted to the DS fender and had a three point plug screwed into it. I am not certain as to how the new harness will connect to the flashing unit, but I know it doesn't have the 3 point plug. The 3 point plug that was on my truck was literally "Hanging by a thread (wire)". I cut it away from the old harness, hoping to find a way to repair it so I can use it with the new harness. I don't know yet if that is possible, but thought I would look at it tomorrow after church. Thoughts anyone??

 

[Barrman]

You get to wire the 3 pin flasher plug into your harness. Along with the I think 7 pin plug at the blinker arm. It will be fun. You get to work with wire A or B or C and match them up to wire 20 or something like that. I have done it several times now.

 

[rmesgt]

You get to wire the 3 pin flasher plug into your harness. Along with the I think 7 pin plug at the blinker arm. It will be fun. You get to work with wire A or B or C and match them up to wire 20 or something like that. I have done it several times now.

Ahh! I figured it would be something like this. Out of the three positions on the flasher plug, one of them goes directly to ground on the frame just below where the flasher module bolts to the fender. I think it is the C terminal... I will find out this week!!!

 

[G744]

Chances might be your new loom is an older version, and doesn't have provisions for turn signals at all. It is easy to add the necessary wires along the existing pathways, and wrap the whole thing in tape again to cover the added wiring.

 

[rmesgt]

OK all…. I have been busy studying both the harness existing in my truck and the harness that I purchased. Thankfully, Mr. Peter Bog created a CAD drawing of the wiring harness for the M35A2. I have been pouring over this drawing for the last several weeks. I went so far as to recreate the schematic in CorelDRAW, which gave me the ability to change wire colors so I could map the circuits. This also gave me an intimate knowledge of the circuits in this truck. With this info tucked into my six remaining brain cells, I was able to figure out what I need to do make the new harness work. Over the next few weeks, I will make the modifications and install the new harness. I am super excited to get this project started… Also, a HUGE shout out to Mike at Big Mikes Motorpool for his knowledge.

By the way.... Does anyone know where we can get the tiny number tags for the wires? My google search hasn't been successful...

 

[Barrman]

I bought a bag of 50 or 100 of those aluminum number tabs off ebay decades ago. Then I ruined a very high percentage of them trying to stamp numbers into the tags but not through the tags. Now I remove old ones off any wires getting thrown out and put them in a bag to search and search and search for the correct number.

 

[rmesgt]

That's what I have been doing as well. I did find a company that makes them, but you have to order hundreds at a time. Fortunately, you can choose the numbers you want stamped into them. With my deuce, I am guessing that I would need about 20 different numbers, but I have never bothered (yet) to list all my numbers.

 

[rmesgt]

Using the CAD file provided by Mr. Peter Bog, I recreated the wiring harness for my truck in CorelDRAW. I have attached it as a PDF to this message if anyone is interested. If you're a CorelDRAW fan, I can send you the source file if you want it. Just let me know.

 

[G744]

Very nice, thanks for publishing that.

 

[rmesgt]

Very nice, thanks for publishing that.

You're Welcome

 

[Jeepsinker]

Did you finish this yet? I did this on my truck and made a bunch of videos on my channel about it. I can lend some advice if needed.

I'll just go ahead and tell you now, for your front axle light all you need to do is run a 3 way splitter from your gauge cluster power wire and use that extra lead to feed the light.

And you don't need that generator to alternator adapter kit either. Strip that leg of the new harness back and connect the large wire to the constant hot side of your starter solenoid, then just use some 14 gauge prestolite wire and a couple connectors to extend the field wire over to the alternator.

 

[rmesgt]

I did indeed complete the wiring harness. I wrote down every step and have built an outline on what to do, how to do it, how long to makes the additional wires, etc. I didn't take any pictures, but I think it worked out pretty well. I was going to create a PDF file from my write-up and post it to my dropbox. I will also post a copy to this message thread. I learned so much about my truck working with this wiring harness. It is remarkably simple and has a total of about 10 circuits. The CAD wiring diagram was an amazing help. While studying the CAD diagram, I did discover what I think is a flaw.

The CAD diagram shows the heater circuit BEFORE the main power switch, which means the blower will turn whenever the blower switch is left in the on position, regardless of the main power switch. To me, this is nonsensical because it would be pointless to have the blower working if the truck engine is not running. I think the blower switch should be dependent on the position of the master switch.... Your thoughts????

 

[Jeepsinker]

I did indeed complete the wiring harness. I wrote down every step and have built an outline on what to do, how to do it, how long to makes the additional wires, etc. I didn't take any pictures, but I think it worked out pretty well. I was going to create a PDF file from my write-up and post it to my dropbox. I will also post a copy to this message thread. I learned so much about my truck working with this wiring harness. It is remarkably simple and has a total of about 10 circuits. The CAD wiring diagram was an amazing help. While studying the CAD diagram, I did discover what I think is a flaw.

The CAD diagram shows the heater circuit BEFORE the main power switch, which means the blower will turn whenever the blower switch is left in the on position, regardless of the main power switch. To me, this is nonsensical because it would be pointless to have the blower working if the truck engine is not running. I think the blower switch should be dependent on the position of the master switch.... Your thoughts????

I'm not sure that's a flaw. They're all like that. Perhaps it's for ventilation without the truck running, Perhaps it's for defrost with the arctic heater or coolant heater installed, or maybe the master switch just isn't rated for enough amperage to support the blower motor and everything else together. It certainly can very easily be wired to only be powered with the master switch on by just reconfiguring a couple of connections though.

 

[rmesgt]

My deuce doesn’t have a heater, so I have no idea if the CAD drawing is correct. I have nothing with which to compare. If I were to install a heater though, I would draw power from the master switch to power a relay only, getting power to the blower motor from an alternate source.