Dark editor window titled F150 showing a wiring layout: several harness trunks with branches to connectors spread around the canvas, and dozens of curved wires converging on a column of plugs in the centre

Desktop appPart 1 of 1Drawing 44.1 of 47

F-150 Coyote harness

The example: a full harness for a 1985 F-150 with a Coyote V8 swap. Ten harnesses, 512 connections, 266 circuits and a fuse box of my own.

StatusWorking, version 0.1.0, 2026
Built withReact, TypeScript, Electron, React Flow
Runs onmacOS, offline
File formatthe open .harness format, read and write
Parts804 in an offline catalog, Deutsch, TE, Molex, JST, Aptiv
Examplea 1985 F-150 Coyote swap, 512 connections

Sheet 02 of 09/Why

Old truck, new engine

A 2015 Coyote and a 1985 truck were never meant to talk to each other. Rather than splice the two together, I'm drawing the whole electrical system again: engine, power, cab, front and rear body, dash and doors.

Sheet 03 of 09/Layout

Ten smaller harnesses

It's ten harnesses instead of one big loom. Each one ends in its own plug, so the injectors, the coils and the engine can each come off the controller on their own.

Connections, circuits and connectors per harness
Harness	Connections	Circuits	Connectors
Engine	95	58	37
Injector	18	9	9
Coil	19	9	10
Power	66	52	32
Cab	45	35	10
Rear	22	12	6
Truck tie-in pigtails	11	11	1
Front body	51	22	21
Dash and doors	131	77	36
Rear body	54	22	19

Bar chart of the ten F-150 harnesses by number of connections, from 11 for the truck tie-in pigtails to 131 for dash and doors, with circuits and connectors listed beside each bar — *PL 01*Connections per harness, counted from the design's own wire list. Dash and doors is the biggest at 131.

Zoomed-out layout view showing several harness trunks with branches spread around the canvas and curved wires converging on a central group of plugs — *PL 05*The full layout at a glance: ten harnesses around the two controllers in the middle.

Sheet 04 of 09/Controllers

Two controllers of my own

The engine side runs from an engine computer I'm designing myself, and the body side runs from my own body controller behind the firewall. The stock switches are kept and spliced in as inputs to it.

Sheet 05 of 09/Parts

Parts you can buy

The goal was off-the-shelf parts and no special cables. The harness uses Deutsch DT and DTM plugs for its own joints, and factory Motorcraft pigtails wherever it meets a Ford part.

Sheet 06 of 09/Fuses

A fuse box I had to draw

I couldn't find a sealed fuse box that fit, so I designed one. It holds 25 fuses and 6 relays, from 5 amp sensor feeds up to 60 amp feeds for the body controller.

Sheet 07 of 09/Method

Drawn by a script

The whole truck harness is generated by a Python script. Every connector, pin and wire lives in it as data, it writes the .harness file and two spreadsheets, and hexis.harness reloads the file live while I work.

Sheet 08 of 09/Hybrid

A hybrid version, parked

There's also a second file with a Tesla drive unit on the front axle: 13 harnesses and 647 connections. It's parked, because three Model S battery modules give about 68 volts and the drive unit needs 200 to 420.

Sheet 09 of 09/Status

Where it stands

It's a design, not a built harness. Some pinouts still need checking with a meter, 43 parts are marked to verify, and the bundle lengths, the transmission and the engine computer are still open.