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M1009 Rear power 24v to 12v modification

antennaclimber

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Having just installed a new HF radio and accessories on the rear radio rack in the M1009, I wanted to convert the existing 24 volt bus bar to 12 volts. And I wanted to have a better location to access 12 volts other than the one near the glow plug relay. It is limited for high current demands and relies on the stock wiring.

The rear bus bar would need to provide a good source of power for 20-40 amps of current draw and I wanted it to be on it's own fuse. Should the radio or any accessories develop a problem (short), the vehicle wiring would not be compromised.

Here is a description of how I accomplished this with out much trouble and minimal modifications to the vehicle wiring.

1. Disconnect the batteries.

2. Remove all the nuts from the positive bus bar studs on the firewall.

3. Remove the wires from the studs.

4. Remove the metal bus bar from the studs.

5. Install a suitable insulating material on one edge of the bus bar about 1 inch from the edge. I used heat shrink tubing but a few wraps of electrical tape would work. This was done for piece of mind knowing that a live electrical conductor is not exposed to accidental shorting.

6. Reinstall the bus bar one hole off to the left so the insulated portion is toward the passenger fender and the stud next to the fuel filter has nothing attached to it.

7. Reattach all the wires to the bus bar with the exception of the factory installed wire that is run to the rear bus bar.

8. Connect the wire to the rear bus bar to the stud that is next to the fuel filter.

9. Install a new wire from the stud that has the rear wire attached to the positive terminal of the front battery. Be sure to install a fuse as close as possible to the battery. I used an AGU style fuse holder and #2 stranded wire.

10. Secure the wires and fuse holder.

11. Reconnect batteries.

This modification is easily accomplished and is easily reversible should you want to convert the rear bus bar back to 24 volts.

It's also a good idea to clean all electrical connections before reassembly.

Attached are a few pictures of my installation.
Karl
 

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stationjj

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Great post Thank You for sharing. This is something I am interested in doing.

I do have a question. When I purchased my M1009 the rear power bus and cabling were missing.

I got a rear power bus from someone on SS. My question is how the cabling run to the rear.
I have a few ideas how, but not totally sure. I want to make it's done neatly and safely.

From what I could tell the military used heavy duty 2-4 gauge wire? Any suggestion on how to replace the wiring to the rear power bus? I want to convert rear bus to 12 volt.

Thank You.

stationjj
 

antennaclimber

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Stationjj
I will try to get a few pictures of the wire routing, length required and cable size later today.

Fridge.
Thank you for the compliment.
Karl
 

ssdvc

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Awesome. Have you tested voltage to the rear busbar yet? I was thinking of buying a 24 volt inverter for that back area, but now I can go out and get a 12 volt one.

Thanks !
 

antennaclimber

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Here is a few pictures of the factory installed rear bus wiring.

I would estimate that it is about 12 feet of #2 stranded wire.

The voltage at the battery and rear bus bar was the same with no load. With about a 10 amp load it dropped approximately .25 volts.
l
 

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stationjj

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AntennaClimber

Thank You for the great pictures on the wiring for the rear power bus.

Did all M1009 come stock with a rear radio bus? I suspect mine didn't as I can't find anywhere the cable might have run.

Anyway another project.

stationjj
 

cpf240

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Mine is an '84, and it just had the cable running to the radio tray with some form or power connector on the end of it. No buss bar(s).

I wound up pulling the cable out, as the engine compartment end was in really sorry shape.
 

antennaclimber

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I owned one that did and one that did not have the wiring.
Like CPF240, one had an attempt at it with a local wiring job.

So I assume that not all of them had the wiring installed.
 

86M10086.2L

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I did this to my M1009 at the beginning of the summer. I use it as a stout 12 volt power source for my boat winch. In the future it will be utilized for other rear passenger compartment accessories.
 

antennaclimber

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I'd like to see your radio and antenna setup, please.

IC7000 HF radio with custom Tarheel HF antenna, CG144 VHF antenna, roof mounted UHF antenna, VHF/UHF duplexer and Motorola power voice speaker.
Karl
 

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Warthog

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AntennaClimber

Thank You for the great pictures on the wiring for the rear power bus.

Did all M1009 come stock with a rear radio bus? I suspect mine didn't as I can't find anywhere the cable might have run.

Anyway another project.

stationjj
The wiring was installed only if the truck had the Military radios. No radios then no need for the wiring.

Ther is even a section of the TM 9-2320-289-20 manual that covers removal and replacement. Sect 4-45 RADIO HARNESS REPLACEMENT

If you look in the TM 9-2320-289-20P parts manual, Figure 38, you will see all the parts and routing of the wires.
 
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peglegwillie

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Fuses

Looks great. Using both ideas posted to run 12 v to rear bus bars. I have two just before rear inner fender both blank. I was going to run 24v to them but inverter I bought is only 12v so plan changed but will use these post to wire bus bars up for Inverter, CD, CB, and Power points! I will place fuses between each connection for protection !!!
 
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