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Cut Main headlight/turnsignal, etc harness- How to fix...


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So a friend of mine this winter got really anxious on a project on his Z and wasnt thinking and cut the main harness that travels from the left radiator opening across below the radiator and back into the engine bay. I nor my friend know to much about electrical and are not sure about how to fix it. There are 14 wires mostly ~16 gauge with a few larger. Any help for me and my friend...

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LOLz

 

You're friend needs to learn to calm down. :P

 

Anyway.

 

I've had to do this a few times.

Open the harness up, by slicing the tape/covering that is on the harness. This will expose the wires that are in there.

First start by splicing the wires that are coloured the same from one cut end to the other. You can also use wire gauge to match wires. Sometimes there will be two wires (4 ends) that are the same colour(s), but two different gauges, match the gauge. In some cases this takes care of all the wires, in other cases there may be a few circuits that use the same wire colours and a little more investigation is needed.

In the case where there are left over wires, a wire diagram to find the function of each wire will be needed and a DMM (Digital Multi Meter). You can perform continuity tests to determine where that wire goes to, but this can fool you very easily, especially if the harness is still plugged into the car at the other ends. In some instances a few wires will show up with coninuity, even though the wire diagram shows that these should be seperate circuits. The reason this happens is because all electrical devices in the car share the same ground and same positive supply (the battery). Because of this, and the fact that you can read continuity through things like coils (contained/used by relays, injectors, etc), or by filiments (light bulbs), you need to be careful when doing this.

What I usually do is on the end connected to the 'source' I will use the actual switch to check for function. Connect the DMM to the suspected wire, and turn the circuit on, get voltage? Good you have found the proper circuit. No change? Try another circuit (switch) until you find it.

 

Finding the matching wire in the other side may not be as easy and may need to disconnect every wire from the end of the harness and do continuity tests to find where the wires are connected to.

 

Proper connection techniques would include, soldering the connection, taping and heat shrink wrapping the connection. Crimp connectors are only good as a temporary solution IMO.

Depending on how much slack there is in your harness, you may need to add a few inches of wire to each connection, to get everything to fit back together.

You may also want to to add wire to stager the slices anyway so that you don't end up with a large "bubble" where all wires are spliced together at the same point in the harness. I've been working with wires for a couple decades now, so I've now been able to get the slices small and still very insulated so that I only end up with a very small "bubble" where multiple splices are.

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