Installing Aux. 24V and 12V Power and an AN/VIC-4 Intercom in an M35 Truck

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The crew boxes were mounted to the lower channel of the hardtop roof. Engine vibration when idling jiggles the boxes a little, but it is no cause for concern. 1/4" bolts and lockwashers were used to secure the boxes to the channel.

Although they seem to protrude into the window area of the doors, there have been no problems or head-bumping found getting in or out of the truck. The location makes them easy to reach and easy to see if you have to sneak a glance at the switches while driving. Some people have nounted them under-dash, or behind the seats. For this job, the amplifier box is way back in the shelter, andf the interconnect cables are only so long, so this was a good location. The cable between the crew boxes is a 7-FT cable.

The headsets were hung just behind and to the outside of the driver's and rider's positions, and the hooks are military "holder, microphone", NSN 5965-00-295-7481. They can be had for $0.50 to $3.50 depending from which dealer.

passenger's position. The cable from the amplifier unit connects to this crew box, and then a 7 FT cable daisy-chains over to the driver's box.
This image shows the fit of the box in the window area. It doesn't obstruct anything.
Inside view of the driver's station.
The 12/24V cabling was passed through pre-punched holes in the floor under the passenger seat. These holes have caps on them which pry off. On the left, The cables GND, 12V, and 24V come from the battery box to the relay, and the loom carries GND, 12V, 24V, and the relay control wiring under the truck and up to the firewall and into the dashboard.The thick black cable on the right carries GND, 12V, and 24V from the battery equalizer and contactor (relay) to the shelter. The cable is the same as the one on the left except it's covered with heat shrink tubing.
The cable from the contactor comes out from under the cab and heads up to a hatch on the shelter's front. On the back of the cab wall is a foam block holding the intercom cable. The somewhat stiff power cables support the intercom cable well, and they go through a similar foam block in the same hatch. To fit the foam, the size of the hole is measured and the foam is cut 3" wider. The foam is then slit all the way around, and effectively becomes a big gromet with 1.5" extra material all around. The foam is 2" thick.
The hatch was an exhaust vent before. It had a bunch of "Z"-shaped aluminum baffles in the hole to let air out while keeping light and RF inside. These were sawed out and the foam block fitted. To pass the cables through, a "+"-shaped hole was slitted into the foam and the cable ends pushed through. This is temporary and later will be modified so that the hatch can accommodate several SO-239 RF connectors for the radios inside the box.
The wiring was finished up and tied in place. Crimp-on connectors were use throughout, and they are all soldered so there will be no troubles down the road. On the left the cables come up from the battery, along with the loom going to the under-dash wiring. The contactor had two spade lugs on each pole. To accommodate this with the #6 cable, the many conductors of the wire were divided between two 30A spade clips. On the other side of the contactor (switched), two 12 guage wires go from each pole to the battery equalizer. These are the small black wires. -12 guage is a little light, but the distance is very short so there will be no issues. From the equalizer comes the 12-guage wiring to power any under-dash accessories, as well as more #6 wiring to power the shelter's electronics. The blue wire is some computer network cable that was also put into the loom. It's not used now, but this 6-conductor wire might come in handy later to get small signals like a speaker or a small switch to and from the dashboard area.
Shown here, an ON-OFF-ON DPST switch (black underdash panel) was added to allow the auxiliary power to be either turned on manually or switched automatically along with the main power from the truck. The blue lamp indicates that the switched power is ON. The clear lamp above it is for the manifold heater flame detector.
general view of dash
detail of mounting the crew box.
detail of mounting the headset
detail of routing the crew box cable down past the window and door and then further down to the under-seat area. The idea was to keep this expensive 19 FT cable away from the fold-down seat and out of harm's way. On the diagonally mounted brace, a mark can be seen where the seat rests against the brace. It would not do to have the cable loose and getting mashed by the seat.

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