Wire Splices

I have seen several questions on splicing wires so I thought I would share my process.


First, strip the insulation back on each wire 1/2 - 3/4 inch and lightly twist the strands together.



Holding one wire in each hand, cross them to form an "X".


Next, fold the tip of each wire down around the base of the other.  In the instance above, the wire on the left would fold forward and down around the wire on the right.  The wire on the right folds backward and down around the wire on the left.


When complete, the wires should form a nice tight spiral around the base of the other, and the whole splice is not any bigger than the original wire.


Next, solder the wire.  Soldering is an art that takes some practice.  Without going into pages of detail here, I try and get a small drop of liquid solder between the iron and the wire.  This helps with heat transfer.  As the wire heats up, I touch it a couple of times with the solder.  The molten solder will wick into the wire.  I then hold the iron on the wire for a few more seconds to make sure the joint is good and hot, then pull the iron away and allow the wire to cool undisturbed.  The joint should look smooth and you should be able to nearly see the indicidual wires in the solder.  If the joint has a grainy appearance, this is called a "cold joint" and is generally caused by moving the joint before the solder has cooled.  Experiment with this and you will see what I mean.


To finish the joint, slide a piece of heat shrink tubing over the solder joint and heat.  The resulting joint is really no bigger than the wire itself, stronger than the base wire, resistant to vibration and corrosion as well.


This test shows a joint pulled in tension to failure.  Note that the location of the failure is well away from the point of the original splice.

That is really all there is to it.  About the only time *NOT* to use a soldered joint like this is when connecting the signal wire of the oxygen sensor.  The sensor needs a reference to atmospheric oxygen.  Early sensors had a small hole in the case, but it often plugged with dirt and debris.  In a modern sensor, the sensor wire is designed to allow a small amount of air to premeate down it's length.  If you solder the wire, the oxygen can no longer get through the joint, so a well crimped connection is recommended.

Also, from experience, if you need to splice any of the shielded wires, *DO NOT* splice the wire in the middle of the run .  Replace the entire wire with a new shielded wire.  (See my troubles with the distributor code 4!)