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Practical Wiring - Club Level: Step 4: Wire Assembly, Bundling and Branching

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Step 4: Wire Assembly, Bundling and Branching

09.38

00:00 - The fourth step of the HPA eight step process is the one of bundling and organising our prepared lengths of wire into the basic structure of our wiring harness.
00:09 To do this we're going to use simple cable tie mounts and cable ties to build a template on our work surface which is essentially a to scale representation of our harness documentation.
00:20 We'll then begin laying our wires down onto this template, referencing both our physical layout documentation and our connection documentation to ensure that every wires is included.
00:30 The first step of this process is building the template onto which we will lay our wires.
00:35 Now for our workbench here in the studio, I don't want to mark the surface, so I'm going to use blu tack to hold the cable tie mounts in place as this will let me remove them easily once the job is completed.
00:45 I'm also going to use some painter's tape and a sharpie to make a note next to each of the cable tie mounts referencing which point of the harness they represent, be it a branch point or a connector termination.
00:55 I'll go ahead and I'll lay out this template now.
01:31 Right we've got to the stage now where all of our power supply wiring is laid out onto our template.
01:37 Just wanted to pause and have a quick look at our splices up here at the harness section that's going to head to our power supply connector.
01:45 This is one of the reasons I really like to prepare all the wiring and splices beforehand as when they're laid into the template is has made it really easy to stagger the location of all these splices.
01:55 It means we're not gonna get a big bulky point in the harness here that would reduce the flexibility and also be quite visually unappealing.
02:02 Another thing I've done is I've actually located these splices a fair distance away from where our power supply connector needs to be.
02:10 We're going to incase all these splices in a section of dual wall heat shrink.
02:15 And that's going to strain relieve them and ensure that they're going to be really nice and reliable and then we're actually going to have the bare section of wires heading off to our power supply connector.
02:23 Now that's gonna be OK in this situation as it is the interior of the vehicle.
02:27 And it is also a sealed connector so we're not gonna get any ingress in there.
02:31 The extra length of wire is actually gonna make the job really easy when it comes to pinning that connector as we're gonna be able to route all those wires into the correct location in that connector far more easily.
02:42 So what I'm gonna do now is I'm going to progress through the rest of our prepared wiring, so that's going to be our sensor supply, sensor ground wiring, our power ground wiring, then actuator commands and signals and our communication wiring as well.
02:56 Gonna lay it all on the template and get everything out here on the bench and then we're gonna have a look at how we're going to bundle it up, using some kapton tape to keep it all in place for the next step of the process which is going to be sheathing.
03:40 With all of our wires now laid into our template, we're going to use some kapton tape to secure them in position and finalise the location of our branch points ready for the sheathing step.
03:50 Now once again, cable ties should be being used a disposable at this step, they're really gonna help us keep all of the wires in the correct place while we get everything taped up.
04:00 Now I did strike one detail when I was fitting the wires to the template here, and it was to do with the fuel pump wiring.
04:07 We've specified 12 gauge wiring for our fuel pump as we're anticipating upgrading the fuel pump in the vehicle in the near future and we're going to need that extra current handling capacity.
04:16 The fuel pump wiring needs to come from our power supply connector here, back out to our fuel pump connector which is also in the interior, that then heads off via a sub harness down to the fuel pump itself.
04:27 That means it needs to come down to this branch point here, and do a 180 degree turn and head back out to that connector.
04:34 Our 12 gauge wire is not really going to make that 180 degree turn in a particularly compact way, it's going to give us quite a bulky point at the harness here which is not really what we're after.
04:45 So I've gone about it a slightly different way, I've cut that wire in half and then I've used an open barrel splice to join it back together from the same direction and that's going to give us our nice compact 180 degree bend, which is going to get our wires where they need to go.
05:00 Now I do need to go ahead and insulate this with some raychem SCL, keep that nicely strain relieved and seal away that splice as well.
05:08 We've shown this in a few other places in the course, the procedure is exactly the same here, I'm gonna go ahead and do that now.
05:18 With that open barrel splice join sealed away underneath our SCL, we can install this last piece of wiring into our template here and get our power wire up to our power supply connector and our fuel pump wire where it needs to go there.
05:34 So to show the bundling or the taping process in detail, we're going to have a look at our first engine bay exterior branch point.
05:41 So this is the first branch point after the wiring harness enters the engine bay where it heads off to all the various components and the trunk carries through to the other branch points.
05:50 Now what we're going to do here is use some kapton tape to organise these wires, keep them all together and actually add a wee bit of support to this branch point.
05:59 However we want to put that kapton tape onto the harness around about 25 millimetres back from our final desired branch point as that's going to give us enough space between our tape and our desired branch point to organise all of the smaller sections into the orientations that we require, and we do that to match our documentation and to ensure that when the harness fits the vehicle, it fits it nice and tidily and all our smaller harness sections don't need to cross over one another as they head off to their individual components.
06:27 So I've got some pre cut sections of kapton tape here.
06:30 I'm going to get one of those in place around about that 25 mils back from our branch point and because I've got these cable tie mounts blu tacked onto the bench I can actually easily pull that up to get the kapton tape underneath.
06:44 We can get that in place nice and tight.
06:49 Now with that one piece of kapton tape there, what I normally like to do now is actually get the role of kapton tape and put a wee bit more around there just to give it a bit of extra support.
06:57 So I'm gonna go ahead and do that now.
07:04 Now that we've got that branch point bundled from this end, we do have to do the same from the other side of the branch point.
07:10 So I'm going to have a look at this central trunk section of harness which continues on from this branch point and we're just going to support that with some tape as well.
07:18 Once again a distance away from where we want that final branch point to actually be in the harness, just to give us a little bit of room to organise all these branches as they exit that branch point.
07:29 So got some more tape here, and gonna get that in place.
07:33 With everything still here cable tied down to the bench, keeping all our wires where they need to be.
07:44 The rest of the process is very much the same, we're going to go through and use some tape to support all of our branch sections and finalise their locations, so that's going to be on every harness section that heads off to a connector and/or our trunks and our other branch points as well.
07:59 While I'm doing this, I'm going to trim off all the temporary cable ties that I've used as the tape is going to take their place and keep the structure of our harness intact and that's going to leave it ready for the next stage of the process which is going to be sheathing.
08:14 So I'm gonna go ahead and do that now.
08:46 So we're not at the end of the fourth step of our HPA eight step process.
08:50 Bundling and branching is completed.
08:52 We've got every wire in our harness laid in place and our branch points have been finalised as we've bundled the harness up with that kapton tape.
09:00 A couple of details to point out here, as we've finished our bundling and branching process, I have removed all the wires from the template that we had set up on our bench here, and I've actually removed the template as well.
09:11 Now I have gone ahead and used some painter's tape on the end of our branch sections and just written on them with a sharpie so we can remember what this branch was so it doesn't get confused with all the other wires in the harness.
09:23 Now we're going to move onto the next step of the process where we're going to sheath the harness.