66 C10 New Wiring Routing

[Afirehawk1]

Trying to find how the wiring routes in the following areas.

1) Engine harness from starter to alternator.

2) Interior light. Appears to go from fuse box to the back side of the door jamb. i found some clips there. Does the wire travel down/thru the channel under the kick plates?

3) Rear lights, etc. No idea how it goes from fuse box under the dash to the rear?

Any good drawings or photos for reference.? thanks Keith

[ray_mcavoy]

The factory assembly instruction manuals have some wire harness routing illustrations in them.

The under-hood wiring is divided into 3 harnesses. There is an engine harness that plugs in just off to the passenger side of the firewall and runs down to the starter. A clip secures this harness to one of the bellhousing bolts. This harness also has branches that go to the ignition coil and to the switches for the hot/cold & oi lights (or to the temp sending unit for factory gauges). Then there is a headlight & alternator harness that plugs in over on the driver side of the firewall. That harness is clipped to the driver side inner fender well and has a branch that goes over to the alternator. The forward part of this harness connects to the external voltage regulator, horn relay, and includes the headlight connector that plugs into the headlight harness behind the grille. And finally, there is a front turn signal / parking light harness that also plugs in over on the driver side of the firewall and runs up along the bottom of the hood.

Yes, the wire for the interior dome light runs from the fuse box, down through the channel under the door sill plate, and then up behind the rear door jamb, and up into the roof.

There should be a round hole in the firewall a few inches above the gas pedal area. One end of the rear intermediate harness fits into that hole and plugs into a mating connector on the under-dash cab harness. 66 will also have a single light green wire for the reverse lights going through it's own smaller hole just below the larger hole for the other rear light wiring. From there, the intermediate harness runs down the outside of the firewall and along the underside of the cab's toe board area. It is held in place with some clips. The uppermost clip fits into a small hole in the firewall while the lower clips are simply metal tabs that are spot welded to the cab. Once the wiring reaches the lower part of the cab's toe board area, it drops down to the frame where it runs all the way to the back along the inside of the frame's C-channel. Several clips (snapped into holes in the frame) secure the intermediate harness along the way. Near the back of the truck, the intermediate harness plugs into the rear light harness which is clipped to the inside of the bed's rear cross sill.