Learning How to build a loom

Gentlemen,

I just finished the Fundamentals and Club level training. However, I still seem to have more questions. Perhaps i'm stupid of the practical harness building methodology just went over my head.

In the training video Ben Lays down all the power cables....then says rinse and repeat or something along those lines. Some of the power and power ground cables make a 180 degree turn but doesnt explain where they are going, what they are doing? Same with all the terminations going on the connectors.

Time lapse to this...which i was not able to keep up with at all. There's no detailed explanation of what wires are going to which sensors etc? which sensors require more than just a power and ground?

I would rather attempt to understand this and build my own harness for my rx7 instead of asking for a refund. Same thing with the terminations and connectors, there's not enough detail for me to confidently follow it through on my own. It took me minute but I learnt how to tune the rx7 via HPA and have so im not super stupid...but def staring to feel like im not getting the basics of this course despite going over it a few times.

For each connector (sensor, solenoid, injector, coil, ECU, etc), you are going to need to understand the pinout. What pins are ground (to be connected to either a ECU sensor ground, or the chassis ground), what pins carry voltage to the sensor (and what voltage, 5V, 12V, something else), and what pins are signals (either from a sensor to in input on the ECU, or from the ECU output to control a coil, injector or solenoid.

Usually wiring diagrams from the ECU manufacturer may give you hints about where to get the 5V power for a sensor, or what sensor share the sensor ground. This is the point you create a spreadsheet with each connector listed, and where the wires from that connector need to go. For example, you might have a MAP sensor where pin2 (signal) goes to the ECU say pin 12 which is AnalogInput 1. So on the ECU pinout, pin12 would list connects to MAP-2, and MAP pin2 would list ECU-12, this is a good time to pick a wire color.

It's likely you will have several devices that need 12V (either Ignition - switched power, or power all the time). You connect these to a splice point (usually located near the ECU connector, and leave one or more leads to be connected through the fuse box, relay or PMU/PDM device.

I hope that helps.

If I recall correctly, the fundamentals course explains how to wire common sensors and actuators. In the pratical course, there are example of connection documents that you'll need to create. Remember, the most important part is the planning!

In the first image, the tags have an abreviation used by the person making it (you may prefer to write it in full) of what they're for - sensors/senders, or whatever.I would agree that it would have been a smart move to tag each end to avoid wasting time matching the ends.

The 180 bends serve two purposes - the tags are less likely to fall off, and it's a little extra wire length in case they were measured too short.

In the second image, there are two, or more, wires to each sensor/sender because there will usually be a need for a full circuit, and often at least one more.

As David and Frank said, normal practice would then be to look at the ECU pins, and what they can do, and make up a wiring chart (you can usually d/load them from the manufacturer's web site, or a generic one from a GOOGLE search) matching the wires to the pins, and you could add that information to the tag at that end to save having to continually referring to the chart(s).

Once you've done a few wires, you should see there's nothing to worry about - just needs paying attention to what you're doing.

Gentlemen, Thank you. it is very helpful. I need to get this into the design stage and start planning etc...I'm the kinda guy that learns while physically doing stuff and having it in front of me.

I think most of the technical stuff in the videos has gone over my head because there is a lot of theory explained in those 2-3mins short videos with not a lot of practical or visual demonstrations of how for eg. sensor wiring works, how this will differ to say a coolant temp wiring and what wires will go where. Again im sure its all there and you guys are probably thinking this is soo simple...but in my mind its still like a maze...im trying to figure out.

I am a complete novice, doing my first project. At the moment I am past the planning/theoretical stage, doing the assembly.

From the experience I have gathered, I would say you are going about it from the wrong direction. Having the thibgs in front of you is how you will spend money on things you don't need (ask me how I know).

Get a notebook, put everything down on paper. All the loads, sensors, every component. Divide them into groups that make sense. Then do loads of research about pinouts. Your ECU pinout and every component used. Most don't need power supply, because they get the +5V (sensors for example) all from one single pin on the ECU.