Project Lexus SC300 Road Racer: Part 10 – Finish Wiring the Back and Prep the Front Harness


Designing the label is relatively straightforward.

Relatively- it’s not entirely intuitive. The instructions are a little lacking. Figuring out how to sent font sizes was easy, but adjusting spacing and label length was not so easy. In fact, getting a “sensible” length and margin was somewhat frustrating.

The touch-screen XTL 500 was much easier to use and navigate. Unfortunately, both labelers produce labels with a lot of waste. If you want to reduce the waste, you have to get creative with combining labels together. However, you end up spending time fighting with the spacing and margins in order to make it all work out in the end.

I wouldn’t care so much about the waste, except that the label tapes are very expensive. If I was a professional shop and this was for a customer car and the cost of labels was wrapped into the cost of harness design and construction, it would not be a big deal. For a one-off, personal use kind of situation, every penny counts, so I tried to be mindful.


Put the label onto the harness bundle before you pin out the connector.

Much like with heat shrink tubing, you want to select a label that is as small as can be but will still fit over the bundle easily. With that criteria in mind, you will almost never find a label size that will fit over the connector and still be a good size to shrink onto the bundle. That means you have to remember to slide the label over your bundle before you pin out the connector! Let’s just say there are a few things with missing labels because someone that isn’t named Tom who might have a name that starts with Erik might possibly have maybe forgotten to print a label before the connector got pinned out. Maybe.


Heat shrink labels work just like heat shrink tube- you heat them to shrink them.

Labeling all of your connectors helps with harness installation and removal. It also helps identify what is what. It seems trivial, but it’s important. Especially if you are making the harness for someone else to install later. In motorsports, it is very common for someone to design the harness, for a second completely different person/company to manufacture the harness, and for yet a third person/company to install the harness.

If this trunk harness showed up and there are two 6-pin DTM connectors and one is for the right lamps and one is for the left lamps, which is which? You might figure it out once you laid out the harness into the car in a way that made sense, but without some kind of diagram or, preferably, labels, it might not be fun or fast.


That is some sexy harness work.

Once bundles are twisted, your heat shrink is applied, your labels are applied, and your connectors are pinned, your harnesses really start to look sexy. And, we all build race cars because we just want to show off how cool they look, right? At least in this case, sexy means functional and reliable.


We had discussed bringing all grounds to a central point, and this is what it looks like.

In earlier segments we talked about grounding and ground loops, and how important it is to bring all of the grounds in one area of the vehicle to a central point. The old “German” engineering way to do this would be lots of individual ring terminals on a stud. The “American”/motorsport way to do this is to bring all of the ground wires into a single ring terminal.

I don’t know if either is right or wrong. The one caveat to lots of wires in a single ring terminal is making sure that the crimp “captures” or secures all of the wires. You don’t want any individual wire to come out of the crimp and therefore lose ground connectivity. However, it would be relatively easy to identify/find. Using glueline shrink is also helpful in acting to retain/capture the wire inside the terminal.

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