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Club level harness with circular bulkhead connector

Practical Motorsport Wiring - Club Level

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Hi There,

I recently took the full club level course and practical wiring course. I know the Motorsport level course covers the circular connectors, but I did have one question regarding where to start when you have one of these in the loom. Do you still cut the wires to length then lay them out and start doing the branching and then pin into the circular connector when it’s all done. Or in this case do you cut the wires to length, pin the circular connector and then start laying the full loom out into the branches etc? I have all my materials ready, documentation done, and it all drawn up, but I can’t decide which is the right way to go at it with this connector in mind.

thank you for any assistance you have to offer.

You basically build two harnesses, one on each side of the bulkhead. Do them separately.

Thanks David, I think I got that part figured out, but my main question is should I start by pinning the circular connector first and then lay out all the wire into its branches. Or do I still lay out all the branches and then pin the circular connector last.

I pin the circular connector last on the engine side, and first on the ECU side.

Seems to be an either or situation. Most if not all the concentrically twisted harnesses I have seen people build start by pinning the connector then twisting out from there. In the club level course they favor terminating after the harness is sheathed. I don't really think it matters, the only thing that is going to matter is keeping an eye on when you sheath certain parts of the loom before continuing.

Yeap, Brian and David are on point here, it is a little bit of 'make it work' situation, just be sure you're not painting yourself into a corner when it comes time to sheath things.

Sorry to hijack the thread, but I have 2 related questions:

When pining these big connectors (although it seems to be even worse with large rectangular-shaped connectors), do you cut all the wires the same lengths? It seems like some wires will have to be significantly longer than others, and when I tried that I cut them too short... I then tried cutting only the wire I was pinning at the time, which worked a little better, but not much.

That leads me to my other question: I have a situation which I believe is fairly common, I'm building a harness with 2 ECU connectors have to be very close to each other and a bulkhead connector. The harness is somewhere in between what is presented here as clublevel and professional (deutsch connectors, HDP20 bulkhead connector but twisted). For the twisting it seems better to start from the bulkhead connector, but getting the right positioning for the ECU connectors was also tricky in the last harness I built. How does one pick where to start? Is it only a matter of experience to be able to get the perfect length for the connectors?

I have finally settled on this for connectors with more than 30 wires:

I cut the shortest wire first, and measure it from a known location (end of sheathing, wire tie, etc). This might be the center wire of a circular connector, or one on the side of a connector that goes off at 90 degrees. Then I make each additional wire longer by enough to cover the addition distance travelled (might be 1/8", might be 3" on an ECU connector. I work my way from shortest to longest wires, increasing my measured distance as I go.

So, I generally cut one wire at a time, strip, terminate and insert before moving to the next one. I might do two or three related wires if they are in a shielded cable for example.