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Practical Wiring - Club Level: Step 3: Wire Preparation and Splicing

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Step 3: Wire Preparation and Splicing


00:00 - The third step of the HPA eight step harness construction process is to prepare all of the wires which are going to form our harness.
00:07 This involves cutting to length every piece of wire that we're going to need and then performing any splice joins that need to be made.
00:14 I find it best to prepare all of our wires this way before we start organising them into our harness sections and branches, as it lets us confirm that we've got all of the required materials on hand, and is a good opportunity to sanity check our design as we're preparing those materials.
00:29 As an example, if you're preparing the boost control solenoid wiring, as per your documentation, and you've cut the actuator command wire to length but you don't have a matching power supply wire cut to length, it's easy to spot this oversight and correct your design.
00:43 Mistakes do happen and this is a really good opportunity to catch them, as they're very easy to correct.
00:48 I've got my physical layout documentation on the bench here along with my connection document so I'm now going to go through all of the connectors listed, cutting each length of wire as required, storing them in labelled bags to keep things nice and tidily organised.
01:32 Now that we've got all of our wire sections cut to the correct length, we can move onto the next step of the wire preparation process which is performing our splice joins.
01:40 As shown in the skills section of the course, we've determined the location of our splice joins, we can now determine the size of open barrel splice we're going to use and perform the operation.
01:49 The example we're going to show here is the power supply wire coming away from our ECU fuse that then splices out to supply power to our ECU and the auxiliary connectors on the wiring harness.
02:02 So in this instance we're going to take a single 18 AWG supply wire from that fuse connection and we're going to splice it out into five 22 AWG wires, two of which head to the ECU, the other three heading to the auxiliary connector and the two auxiliary CAN bus connectors.
02:18 So we've got our five pieces of 22 AWG wire here.
02:21 They've all been cut to the correct length to reach the portion of the wiring harness they need to.
02:25 We're going to splice those to a section of 18 AWG wire that'll then head off to our ECU fuse.
02:31 To do this we need to calculate the size splice that we're going to need to use.
02:35 So we have our five 22 AWG wires, each of which have a CMA of 700.
02:42 Giving us 3500 CMA there and we can add our 1620 CMA for our 18 AWG wire, giving us an overall CMA of 5120.
02:54 That's going to be in a good sweet spot for our splice size that fits a wire size, wire CMA of between 3500 and 6000 so that's the size we're going to choose for this splice.
03:06 Going to have to strip a section of insulation from the end of all of our wires here.
03:10 Long enough that the copper conductor strands reach all the way through our open barrel splice.
03:15 So I'm gonna go ahead and just get that done now.
03:26 So I'm just gonna get my open barrel splice installed into the end of the crimp tool here.
03:31 Going to use the A size die as I know that is a really good correct size jaw for this application, and we'll just get that centred up and put a little bit more pressure on it just to make sure it stays in place while we are organising our wires to get them in there.
03:50 So we're just going to squeeze all these together, make them a little bit smaller, but once again not twisting them because we don't want to put unnecessary strain on the insulation.
04:01 So get those all installed into one side of our open barrel splice here.
04:06 Making sure none of those copper conductor strands are missed, and checking on the other side we do have protrusion there, so we've got full copper engagement, and then we're going to install our 18 AWG wire on the other side.
04:25 Checking we've got copper on both sides, everything's nice and evenly lined up, and squeeze those handles and undertake our crimp operation.
04:37 So we've got a good solid crimp join there, nice even contact down the middle, a bell mouth, and perform a tug test and that's nice and solid and it's really not going anywhere.
04:48 Gonna go ahead and insulate this now with a section of heat shrink and then we're gonna perform exactly the same operation on the rest of the power supply wires for our harness.
04:59 So you can see with that raychem SCL shrunk down we've got a nice potting bead on either end that's gone good and rigid and is gonna be really strain relieving that splice very well.
05:09 The rest of this procedure is a rinse and repeat of the same process, so we're gonna go ahead and do that now for any of the wires in our wiring harness that require splice joins.
05:36 So now we've completed the splicing for our power supply side of things, that is taking the individual wires from our power supply fuses out to the various items in the engine bay that need that power supply.
05:48 Typically this is going to be between two or maybe three items maximum per fuse, so it's quite easy to keep track of where those wires need to go and which length of wire is heading to which device.
05:58 We're going to do our splice now for our sensor supply, however we've actually got six devices that need to be connected to our sensor supply so we're gonna be taking that single sensor supply pin and splicing it to six wires.
06:11 It's gonna be much trickier to keep track of all the different lengths of wire and which EFI system component they need to head to.
06:18 So to work around this I'm going to take a piece of painter's tape for all of our pre cut lengths of sensor supply wire, pop it on the end here and write down which item that particular wire needs to head to.
06:36 So I've got my oil metering pump position sensor wire labelled now, I'm gonna go through and do the other six here, so that's our auxiliary connector, the engine oil pressure sensor, throttle position MAP sensor, and fuel pressure sensor, and they we're gonna pull all those orange wires out and we're gonna splice them to the single wire that can head off to our ECU connector pin.
07:27 With all of our wiring now cut to length and our splices completed, including any splices made to a shielded cable braid, this brings us to the end of the third step in the HPA eight step process.
07:38 By this stage you should have every wire that will be in your harness cut to length, spliced if needs be and tidily organised for the next step of the process, where we will organise the wires into the basic structure of our harness.
07:50 Now while it would be possible to undertake our splicing as part of our next step, when we're branching and bundling the harness, I find it much easier to do it now, as being able to solely focus on the wires you need to splice, makes it easier to do a tidy and reliable job of the join.