Products

For a 1965 long bed these are the two parts needed:

Wiring Harness Main to Taillight – 1961-66 Ford Truck Part #: C3TZ-14405-ER

Taillight Crossover Harness – 1961-66 Ford Truck Part #: C1TF-13A409-AF

I also purchased some rubber grommets for running through the frame. There were 3 existing grommets, I left one intact and replaced 2. Dennis Carpenter says there are 2 in use on the frame and 2 for the tail light housings. However, I don’t think these fit the tail light housings. The harness i was replacing had smaller grommets attached to the wiring (and not re-useable). I ended up not using any in the tail light housing. I’d wrapped my wire with loom so feel like its protected enough. Here’s the part:

Taillight Wiring Grommet – 1961-72 Ford Truck

I considered purchasing new frame clips. I don’t remember exact count, I believe at least 4 where in use on my truck. However I was able to re-use the existing one and at $4 each, seemed excessively expensive. These are the ones you’d get:

Taillight Wiring To Frame Clip – 1957-79 Ford Truck

I decided to wrap the wiring in loom, since its running along the exterior of the truck, close to the exhaust and I found the tape wrapping on the Dennis Carpenter product was a little sticky. This is what I bought

MGI SpeedWare Woven Mesh Split-Sleeve Wire Loom for High-Temperature Automotive Harness and Home Cable Management – 25 feet (1/4″)

25 feet was sufficient coverage for both wiring harnesses. It was a bit fiddly to put on – and I was worried the 1/4″ diameter loom wouldn’t be big enough, but it was fine, even covering the sections of wiring where there were up to 4 wires bundled.

I also bought some Tesa tape to tape up the ends for good measure, although this was probably unnecessary, the loom doesn’t look like it’ll go anywhere.

Finally I bought some dielectric grease to apply to the connectors just to add some protection.

Layout

At first I thought the harness wasn’t going to be long enough until I realized how it fit together. I also thought the cross-over harness had extra wires, but again turns out just how its designed to fit with the main harness.

My only frame of references was looking at the 1965 wiring diagram. While the purchased harness is conceptually the same, in reality its built differently.

The main harness runs from the engine compartment along the frame. The connector in the engine block has 3 wires – yellow, green and brown.

The main harness terminates with two sets of connectors – a yellow+brown and a green+brown for the driver-side and passenger-side respectively.

The cross-over harness then plugs into both connectors. It has a yellow+brown connector that branches off for the driver side tail light, a longer green+brown for the passenger side. It also has a single bullet connector for a license plate light spliced in. This has continuity with the passenger-side taillight (brown) wire.

Installation

Installation was relatively straightforward. I didn’t even need to jack the truck up. Before starting, I removed both rear taillight housings and disconnected the pigtails from the existing harness.

1. I Fed the main harness 3-way connector up into the engine compartment along the same path as the existing harness and plugged it into main connector.
2. I clipped it into two clips
3. Fed it along the frame rail, cutting out the old harness and placing the new harness in the existing frame clips
4. Then connected the cross-over harness
5. Fed the cross-over harness across the rear of the truck, with the yellow+brown connector up into the driver-side taillight housing and the green+brown connector up into the passenger-side taillight housing.

The connectors were a little hard to push all the way in, using some shop towel for grip I was able to push them together.

Note that the taillight housing has to be properly grounded (i.e. with at least one screw in) before the taillights work. The turn-signal/brakes seem to work regardless. A quick test shows everything now fixed – each rear turn signal operates independently, the brakes don’t freeze the turn signals.

Lastly I created a male bullet-connector with two wires to splice into the pair of license-plate bulbs in my rear bumper. However, I found that the existing bulb sockets were missing bulbs and hard to pry apart, so decided to buy new ones. They’re $5 each.

Here’s what I pulled out of my truck. What a mess.