Continuing on from the last post…
Here I’m beginning to loom the harness with a combination of the fiberglass braid plus short lengths of adhesive tube that will later be shrunk down over the ends of the loom to prevent fraying and seal the wires where the harness splits. You can see that assembling the loom requires a good bit of forward-thinking because each section often needs several more various pieces sleeved over it that will be shrunk down later:
Also in that pic is the bulkhead connector already assembled. That connector contains each wire that will pass from through the firewall into the engine bay, which makes it very quick and easy to disconnect the engine side of the wiring from the car so the engine can be pulled quickly without having to disconnect the wiring harness from the engine.
With beginning to pin wires into connectors we can cover the final piece of documentation; diagrams and pin layouts for each connector in the harness. When I began the harness build this sheet had blank spaces next to each pin, and I filled the sheet out as I assembled connectors:
Looming an engine harness is rather straight-forward as nearly every wire begins at a common datum (usually the ECU). Looming a chassis harness can be a bit more complicated since you have wires doing a lot of back-and-forth from switches to fuses to devices etc. In my case, I planned to put the fuse/relay box and a distribution block for power and ground on the passenger side of the transmission tunnel for easy accessibility. Also along this same area of the harness I had multiple breakouts for connectors that would go to the switch panel. This all made for a dense bunch of splits all at one point requiring a bit of work to tidy up and seal.
Here the wire is as condensed as possible and wrapped in kapton tape, ready for the Raychem ATUM to be slid over and shrunk to seal the breaks:
And with the breaks all sealed up:
After the loom is in place the last step is pinning the wires for the connectors. There are a few popular options for connectors with different strengths. I chose to use the common weatherpack and metri pack connectors for ease of service. Each wire has a seal that is assembled with the terminal so that the wire itself seals to the connector – the benefit here is this eliminates the need to seal the whole backside of the connector. In this pic you can also see the short sections of clear shrink tube that are put on each wire before the terminal is crimped on and will be shrunk over the labels afterwards:
Terminals inserted into connectors, connector sheet updated with which wire went in which pin position and each connector’s name labeled on the loom behind it. These are the connectors that go to all the engine and auxillary control switches that will be on the center console:
Similarly finished ends that go to the fuse/relay box:
There were a few other connector types used for the harness as well. Some were OEM connectors that had to be re-used, and then there was the connector that goes to the Racepack IQ3S dash. This is supplied by Racepack with an extra long pigtail made up of standard cross-link wire. I needed to de-pin the connector and then rewire it with the milspec stuff:
After some digging I found this is a Motec M800 34-pin connector. What do you know, ProwireUSA has pins for those
Here’s the connector, new and improved:
For fuses and relays I chose this trick little combo box that takes both mini fuses and micro 280 relays. It uses metri pack seals and connectors:
Beginning to wire the box:
After much work, here it’s tidied up with service/strain relief loops on each wire:
The finished fuse/relay box and harness. The ring terminals go to a bus bar for power distribution and grounds. I put this whole assembly on connectors rather than build it into the harness so that it can be removed for service or additions without the need to take the whole main harness out of the car:
And after much more work, we’ve got finished harnesses, ready to go to the shop for install.
Main chassis harness (connectors to Racepack dash, OE brake pedal , GM gas pedal, fuses/relays, OBDII, all switches, tail harness, diff temp sensor harness) :
Power and ground to bus bars:
Tail harness (connectors to chassis harness to fuel tank, rear lights, and grounds):
Diff temperature sensor harness:
Engine control switches:
Racepack dash page toggle buttons:
At the shop, everything ready to go in. Oh, and this saves 10 lbs over the old wiring that was the already hacked and trimmed down factory harness:
