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Practical Wiring - Club Level: Splicing Supply / Ground Wiring

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Splicing Supply / Ground Wiring


00:00 - The power supply and ground and the sensor supply and ground wires will need to be spliced out from their single wires near the supply relays or ECU headers, to the multiple wires that head off to the EFI components that they connect to.
00:12 As shown in the wiring fundamentals course, we perform these splice connections using open barrel brass splices and a specific crimping tool.
00:20 We need to put some careful thought into where in the harness we position these splices however to avoid them being subjected to excessive strain or causing rigid points in the harness that can make it difficult to route where we initially intended.
00:33 To avoid this happening I will only ever place splices directly behind a connector or at a branch transition point.
00:39 These areas will be strain relieved and supported with a section of dual wall heat shrink and are the ideal location for our splices.
00:47 This also means that the harness sections between these points are a fixed size.
00:52 That is the number of wires along that section, neither increases nor decreases.
00:57 This helps us keep the harness uniform giving it a tidy appearance.
01:01 To show an example of this procedure I'm going to take our four injector power supply wires and we're going to make a splice join to connect them to a single wire that will be pinned into the power distribution block.
01:13 Now I've chosen 18 AWG wire as the single wire to head to our power distribution module as it's larger size is going to be more capable of carrying the combined current of all four of our injectors.
01:24 The other reason is that the open barrel crimp pins that actually interface with our power distribution block are quite large and we are going to need a larger overall CMA size when we crimp all of the wires to that pin, so using an 18 AWG wire along with the other wires that will be crimped into that pin is going to let us undertake that process successfully.
01:44 Now as in the wiring fundamentals course the splicing operation we're going to undertake begins with calculating the combined CMA or circular mill area of our wires and then determining the size of open barrel splice that we're going to need to use.
01:57 We've got four 22 AWG wires here, each of which having a CMA of 700.
02:01 So we can go four times 700 and we've got a single 18 AWG wire which has a CMA of 1620 so we can add 1620 to that, giving us a combined CMA of 4420.
02:17 Now we have linked below this module to a sizing chart that is going to give you a CMA value for the common types of stranded wire we use in the automotive world.
02:28 So with our combined CMA of 4420 calculated, we can head to our tool kit and select the correct size splice.
02:34 So the size of open barrel splice that I've chosen here is suitable for joining wires of a CMA of between 3500 and So we're almost spot on in the middle of that range and this is going to be perfect for this application.
02:49 So the first thing I'm going to do is get this installed in the end of our tool here with a bit of pressure on our ratcheting jaws, and get it centred up.
02:59 I'm gonna pop that to one side and I'm going to strip some of the insulation from our wires.
03:05 Now the amount of insulation that we're going to strip once again is going to be sufficient that the copper conductor strands will protrude all the way through that open barrel splice, letting us do a really quick and easy check to determine we've got full copper engagement.
03:18 So I'll just go ahead and strip these conductors now.
03:26 Now with those sections of insulation stripped from the end of our wires here, we've got enough copper conductor strands showing that they will protrude all the way through that open barrel splice, it's gonna let us do that quick visual check to confirm that we've got full copper engagement there.
03:39 Now for this splice join it is going to be an in line splice.
03:42 So that means I'm going to insert these four injector power supply wires from one side and a single power supply wire heading to our power distribution block from the other.
03:51 The reason I'm choosing to do that in this situation is that the connector body on our power distribution block is not actually bootable.
03:58 Which means we're not gonna be able to make good use of the strain relief loop.
04:03 Instead what we're going to do is we are going to locate our splice join here right underneath the section of rigid raychem SCL that will terminate our sheathing very very near to our power distribution block.
04:16 So we're going to undertake this crimp join now.
04:19 We're going to get our copper conductor strands all into our open barrel splice there, making sure that they're all in place and protruding out the other side and that no copper conductor strands have been missed.
04:31 We're then going to hold this in place and we're going to get our power supply wire inserted from the other side, once again just confirming that we've got full copper engagement there and everything lined up, we can squeeze our handles and undertake our crimp operation.
04:56 Now having a quick visual inspection of that crimp join, we can see we've got contact down the centre of it, we've got a nice bell mouth at this end and we do in fact have full copper engagement and a little bit of a tug test, that is really nice and tight and that is gonna be a completely reliable join for the life of the wiring harness.
05:13 Now we're going to need to put a small amount of sealing heat shrink on this.
05:17 So we're going to use a section of raychem SCL for that.
05:20 You can install it from one end of our wire here and we can get that in place, centred over that join, get our heat gun and shrink that down.
05:33 Having a look at our splice join now we can see that that SCL has shrunk down nice and tight, it's become very rigid as it's cooled and we've got a good sealing bead at either end.
05:43 That's gonna give us really good strain relief and that's gonna be a totally solid splice join.
05:47 Now usually our power supply, our power ground, and if fact our sensor supply and sensor ground splices will be undertaken as part of our wire preparation step.