- The term splicing refers to using an open barrel crimp connector to join
one or more wires in our wiring harness together.
This could be breaking out a single 18 AWG wire into four 22 AWG wires
that provide power to the injectors on a four cylinder engine,
or taking the single sensor ground pin from an ECU out to the multiple
sensors in the engine bay that require it.
No matter how basic the EFI wiring harness you're building is,
you will almost certainly have to perform multiple splice joins during
its construction.
They can be another common failure point, and we'll look at the processes in detail
to make sure you have the information to complete the job properly.
Open barrel splice joins are very similar to open barrel terminal joins,
but we put them into a category of their own as the tooling requirements
are slightly different.
This is because we use brass open barrel connectors for our splice joins
and these need a very strong and rigid tool to make the crimp operation
reliable and ensure that the tool doesn't flex.
The tool I use for the large majority of splice connections is a ratcheting
type which uses a linkage to provide extra mechanical advantage and thicker
dies to add the necessary rigidity.
We'll undertake a couple of common splice join applications to demonstrate
the key ideas and processes you need to know to ensure your own splice
joins are successful and reliable.
The first splice join we'll have a look at will be joining a single 18 AWG wire
to four 22 AWG wires.
Now this is a splice join you'd make if you were taking a single power supply
and running it out to the four individual injectors of a four cylinder engine.
So our first consideration is the size of the splice we're going to use.
Now there isn't an industry standard agreed upon way of sizing open barrel
splices like this.
There's a few different methods.
You'll see them either sized by the overall AWG of wire they can accept,
the overall cross sectional area of wire they can accept,
or the overall circular mill area of wire they can accept.
The circular mill area method is probably the most common I find.
Which is also a little unfortunate as it's also the most confusing.
We won't go into exactly how to calculate the circular mill area of the wires
we've got here, but I have provided a table below
that lists the common circular mill areas of the wires you'll deal with
most often.
Now the individual 22 AWG wires we have here have an individual
circular mill area of 700.
So if we add the four of those up, we get a combined circular mill area
of 2800.
The single 18 AWG wire has a circular mill area of 1900.
So if we add that to our circular mill area of 2800,
we get an overall CMA of 4700.
These splice joins are rated to join wires of an overall CMA of anywhere
between 3000 to 6000, so we know we've got the right size for the job.
Now as I mentioned, the tool we use for our splice joins is a little bit
different to that that we use for our open barrel terminals,
in that it has a linkage arrangement to give us extra mechanical advantage
and it's ratcheting.
Now it being ratcheting is exceptionally handy because it means you can put
the crimp splice in place and then ratchet the tool down to apply
a little bit of pressure and hold it.
Like so.
And this is really really handy as it can be a bit of a struggle to line everything
up and then hold it in place to perform the crimp operation.
When we get to this point, the aim is to get the four 22 AWG wires
into one side of our open barrel splice.
Ensuring that all the copper conductor strands are all the way through the splice
so none of them are to be poking out the side.
We then need to get the 18 AWG wire into the other side of the open barrel
splice like so and with everything in position,
we can apply pressure to the handles and complete the crimp operation.
Now the size of die that I've chosen here to do this crimp operation,
once again is a bit of a trial and error process to determine.
I know that with these size crimps, I use the A size die with this tool.
I've got that documented in my tool kit.
With the crimp operation completed, we can perform our optical inspection.
So we're looking for those upper tangs of the open barrel crimp
to be evenly folded over and gripping the wire tightly.
We can perform our tug test, make sure nothing in there
is gonna be loose.
And a properly completed open barrel splice join like this is actually stronger
than the substrate wire itself.
You could put this in a machine that would test it and it would apply
pressure until something breaks.
And the thing that would break first would actually be the wire
and not the join itself.
So with the crimp join completed, we do have a section in the middle
of our loom here that's uninsulated.
And particularly in this application, if this was an injector power circuit,
it would be uninsulated and being supplied with 12 volts,
which would never be a good thing.
So we do need to provide some insulation there.
And we do that using dual wall heat shrink.
In this instance I like to use Raychem SCL as it provides a very tidy
and neat appearance and when it's fully recovered,
it is very rigid which provides great strain relief to the join.
So we can heat shrink that down now.
So with the heat shrink fully recovered we can do another quick visual
inspection.
What we're looking for is that we can see a nice even bead around the ends
which is the dual wall of the heat shrink that has sealed up on the wire there.
So we know that's fully insulated and it's providing good strain relief.
This is a successful splice join and it's not gonna fail any time in the future.
The next splice example we'll have a look at is joining a single sensor
ground wire to four individual sensor ground wires.
This is really common to have to do as most ECUs are only supplied
with a single sensor ground pin, and you do need to run this to all
the sensors in the engine bay of the vehicle.
So the first step to completing this splice join is the same
as the previous one.
We need to work out the overall CMA of all the wires we're
joining together.
So in this instance it's five 22 AWG wires.
Now 22 AWG wire has a CMA of 700, so five times that 700 is 3500 CMA all up.
Now 3500 falls into that 3000 to 6000 CMA range of the same size open barrel
splice we previously used.
So we can use the same size again.
So once again the procedure is very similar.
I like to open my crimp tool here, and we're gonna use the same size die
as I know that's the correct size to be used with these open
barrel splice terminals.
And we'll ratchet it down to apply just enough pressure to hold it in place.
This is where the procedure differs slightly from the last open barrel
splice that we performed in that when I'm making a connection like this,
I like to do it all from one side and I'll explain the reason for that in a minute
when we've completed this join.
So we need to insert these five 22 AWG wires all into one side
of this open barrel splice.
Which we've got them in there.
Just double check there's no copper conductor strands that have been
missed, there's none sticking out the side which is excellent.
So we can provide pressure to the handles and complete the crimp operation.
And then we can start to perform our initial visual inspection.
So same thing we're looking for here, is the upper tangs of the open barrel
crimp are evenly folded over and everything is tightly gripped.
It's a little bit trickier to perform a tug test here but if you get
your fingernails behind the open barrel splice and tug on the wires,
you can ensure that everything is nice and tight.
Now the reason I like to perform an open barrel splice join all from one side
like this when we're going to be close to a connector body,
is that when we take this wire around and pin it into our connector body,
we're left with a strain relief loop here which can be really really handy.
And then it gets hidden beneath the boot that goes on the wiring harness,
that connects to the connector body.
So we do have the same issue as before however, we do need to insulate
this crimp join as you can't have a section inside your wiring harness
that is uninsulated.
So we'll do this with some heat shrink again, pop that on there,
and heat over to our heat gun.
So with our heat shrink operation completed we can undertake
a quick visual inspection.
You would've seen me do something slightly different there at the end
of the heat shrink process.
I closed up the end of it with a set of flat jaw pliers.
It just gives a very nice tidy appearance and makes sure the end is fully sealed.
So we're again looking for the nice even beads of the inner dual wall
adhesive around the wires showing that it is well sealed.
And that it's gone nice and rigid and providing excellent strain relief.
So we can see when we bend this wire around and then pin it
into our connector body, we're gonna have a nicely strain
relieved join.
So the two demonstrations we've undertaken here do cover
the majority of splice connections you're going to make when
constructing a wiring harness.
If you strike any other situations and you're a little unsure however,
create a topic in our online forum, and we'll do everything we can
to assist.
Also on our online wiring forum, we've got links to suppliers,
where you can purchase the brass open barrel splices,
and the details on the tool I use here.
That was just one of the 65 modules from our EFI wiring fundamentals course,
which is the perfect place to start if you're interested in learning how to design,
and build EFI wiring harnesses.
This course will teach you the fundamental electrical principles that you'll need
to know, how to select the correct materials to ensure they can withstand
the automotive environment, the wiring requirements of different
sensors and actuators, and how to design a power supply and grounding scheme
that will protect the harness in the case of a component failure.
You'll learn how to correctly splice and insulate connections, how to bundle
a harness and then sheath it to keep it tidy and protected.
For more information and to purchase the course, click the link now.