Project SC300 Road Racer: Part 12 – Cabin Fever


Man, this thing has a lot of stuff going all over.

Here’s the cabin harness, with no connectors, but essentially all assembled.

The cabin harness has a big mess of grounds for everything in the cabin (we talked about the importance of grounding everything in the same spot in previous segments). It has a couple of legs for the two connectors on the Racepak. It has a leg that goes into the ECU. And it has various spiders that go to all different parts of the cabin – the front firewall, the dash switch area, the data logger, the dashboard, and so forth. Also, not pictured, is the big long leg that goes to the back firewall. And, don’t forget, the wheel speed sensor harness is completely separate and isolated.

Whew! That was a lot of work.


Time to get started wiring up the switch panel sub harness.

For whatever reason I used a combination of standard toggle-style and Carling Contura switches. The latter uses push-on 0.250” connections, and the former uses small #6 ring connections.


Since some of the steering motor power wires were connected to multiple terminals, it was relatively easy to have two of these small 20AWG wires crimped in one.

It’s not necessarily a best practice, but these are not mission critical wires and are easy enough to get to to repair. You can also see the ring terminals starting to go on.


It’s a good idea to shrink all of these terminals as best you can, to prevent accidental short circuits.

It’s also a good idea to glue and or boot the entire back-side of the switches, but then you are never going to get that stuff out, ever.

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