How to Modify Vehicle Wiring - Starting with the DO NOTs

[Big_Geek]

Poor practices in adding/modifying vehicle wiring systems is a pet peeve of mine and I see it quite frequently in do-it-yourself articles as well as instruction manuals from respected off-road manufacturers. I will readily admit that I am a bit dogmatic about wiring systems and making sure they are rock-solid. If that is not of concern to you, go right ahead and do whatever you think is best. If you are willing to invest a little extra effort into your wiring efforts, I'll take you through what I have found to be the best wiring methods to ensure a secure and reliable wiring system. I'm not sure if this is already covered here, but I'm going to break this down in a few posts as I continue modifying my Tacoma.

Let's start off with a few "Dont's" of vehicle wiring:

1. Quick Splice Connectors



Never use these. I don't often say never, and I could be convinced that there are emergency situations where this would be appropriate, but I'm not aware of any. Having said that, there are several problems with these connectors - the first being that they destroy the weatherproofing of the wiring jacket and do nothing to replace that seal. This leads to corrosion of the wire and, over time, poor connection to whatever you are attempting to splice in. The second problem is that they often cut individual wire strands in the original wire upon installation. This reduces the number of strands that are capable of carrying the electrical load of the system and can cause heating in the wires, or failure of the connection. The third is that, over time, these connectors can continue to cut away at individual wire strands and further weaken the original circuit into which you are splicing. I was a bit shocked to see my new bumper lighting kit from a very respected off-road manufacturer included these as part of the installation kit.

2. Butt Splice Connectors



Again, never use these. The fact that you're reaching for one likely means that you should be reaching for a soldering iron and heat-shrink tubing instead. These connectors are mechanically and electrically poor (and continue to degrade on both counts over time), they are not weatherproof or even weather resistant, and are prone to failure at the least opportune times.

3. Crimp Connectors



Don't get me wrong, I love a good crimp-on connector, but there is a right way (detailed later) and a wrong way to use them. If you follow the instructions on the packaging and only use mechanical crimping force to secure the connector, you are asking for intermittent electrical problems as well as potential connection failures. This could lead to inconvenience, blown fuses, or (worst case) electrical/battery failures.

Here is an example of what I see with crimp connectors that drives me bonkers:



I'm sure the creator of this configuration is perfectly happy, but I see twelve opportunities for electrical failure added into this circuit (two crimps on each butt splice, plus another crimp on the female blade connector).

4. Connecting to a Power Source Without Circuit Protection

Unless you are installing a device that consumes an incredible amount of power (such as a winch), never connect to the battery without a fuse, fusible link or circuit breaker. In most cases, to make this happen, you actually have to cut off a fuse holder that the manufacturer installed.

5. Weatherproofing

If a connection is installed outside of the cabin of the vehicle (and sometimes even inside the cabin), you really need to consider weatherproofing that connection. This can be in the form of solder, heat shrink tubing, a combination of the two, electrical tape (often the least elegant solution), or weatherproof connectors.

This is a weatherproof connector:



Again, my bumper lighting kit came with non-weatherproof connectors, so I will be cutting those off, sliding on the rubber "gaskets" in the picture, stripping the wires, crimping AND soldering the connectors, installing them in the housing, sliding up the gaskets, then clipping down the plastic cover to keep everything in place. The total cost will be somewhere in the $15 range to fix both sides of the bumper which is a price I'm very willing to pay for peace of mind.

Please feel free to add poor wiring practices that I have omitted. In the next installment, I will start showing my preferred way of splicing wires and installing connectors.

 

[overlander]

Early in my automotive customization life I used quick splice connectors on my CJ7 mods and repairs, and they haunted me with intermittent faults for years to come. They are plastic manifistations of the devil himself and I have since rid myself of them in my kit and all my vehicles.

I would add:

- that one thing you never want to have when you do electrical repairs is a lack of time. Do not rush electrical jobs. the shortcuts you end up taking to get it done will almost always come back and bite you!
- know the amp draw you need to support and determine the right gauge wire for the job. if you are short hand and can't wait, go bigger, not smaller.
-try to be consistent with the wire colors. it makes diagnosis down the road much easier. for example, on my 110, yellow always means it's tied to my 2nd aux batter positive (with no dual usage to any factory harness colors).

Good job OP

 

[southpier]

not sure if you're looking for feedback in this thread or it will be a tutorial, but here goes:

why not crimp connectors?
how do you solder crimp connectors?
does heatshrink go over the crimp connector @ the wire entry end?
and will this be acceptable?
don't soldered connections crack from vibration over time, and then become a potential intermittent short?

obviously, electricity is not one of my strong points. when we're all calm, i'd appreciate someone explaining why I need a relay when replacing my factory horn!

thanks

 

[phydough]

Sadly some folks use the "snip-strip-mash-twist-wrap (maybe) with electrical tape or duct tape" method. I was given a free car that had an alarm installed this way. I ended up rebuilding most of the harness because the deeper I went, the more problems I found.

 

[pugslyyy]

I have to take issue with the 'no butt-splice connectors' and 'no crimp connectors' - there are places for these when done right, with the right connector and the right equipment.

The telecom world is held together with 3m scotchlok butt connectors, and it is harder than you might think to solder wires together.


In the example shown (crimped spade connectors on the back of a switch) are you seriously suggesting soldering it???

http://www.expeditionportal.com/forum/attachment.php?attachmentid=180321

 

[psykokid]

While soldering is right in a lot of applications, it doesnt tend to do well in the long run in automotive apps. Especially in vehicles like ours that we take and run down miles of washboard roads that will vibrate your fillings loose. If you look at a lot of the automakers factory repair manuals, you RARELY see them mention soldering anything in the wire repair section. Other than a few examples of welded points in a wiring harness I recall seeing in the past, all MFG's use crimp connectors. Using bare metal butt connectors, a quality set of crimpers for the type and size of connector you are using, and then sealing with properly sized self sealing heatshrink is the way to go.

FWIW HERE'S a good link to the VW SELF Study guide for wiring harness diagnostics and repairs. Alot of this info is applicable to any automotive..

 

[GhostRing]

why not crimp connectors?
how do you solder crimp connectors?

I am NOT an electrician, so this is worth what you paid for it...

I feel the classic auto parts store box of yellow, red ect. crimp connectors do a crummy job of
correctly grabbing the wiring AND the sheath. I personally like (correctly) crimping when possible...

This is the type I prefer to use

 

[southpier]

and then heat shrink over ???

 

[pugslyyy]

and then heat shrink over ???

I use the 3M/Ancor connectors that already have heat shrink over them and adhesive inside. Heat gun melts the adhesive and shrinks the tubing to fit - once you are done it is a permanent and waterproof connection.

 

[mvbeggs]

I use the 3M/Ancor connectors that already have heat shrink over them and adhesive inside. Heat gun melts the adhesive and shrinks the tubing to fit - once you are done it is a permanent and waterproof connection.

:iagree: on the 3M/Ancor connectors.

 

[Silver dude]

Please feel free to add poor wiring practices that I have omitted.

Acid core solder= not for use in electronics. The acid can eat circuits off a printed board. Being acid based it tends to corrode wiring.

Solid core household wire like romex. Its not stranded it can't flex. In a mobile application full of movement and vibration the wire needs to flex rather then crack.

Using improper wire gauge. A 22gauge wire isn't enough to take a 200amp circuit. Don't extend factory wiring with a smaller then factory gauge wiring.

Don't skip installing relays because you don't know how. They are simple yet important devices use them!

Installing wires in a sharp or possible chafing area without some sort of wiring covering or proper routing.

 

[I Leak Oil]

The general premis that crimp connectors are inferior is not accurate. A quality connector installed in the right way with the right tool is everybit as good, in some cases better then a soldered connection.
In most cases I would guess that the joint fails because of how it is installed, even with the cheaper auto parts store units.

 

[southpier]

...FWIW HERE'S a good link to the VW SELF Study guide for wiring harness diagnostics and repairs. Alot of this info is applicable to any automotive..

I just skimmed this document; great detailed information; thanx

...Don't skip installing relays because you don't know how. They are simple yet important devices use them!

...

any chance you could elaborate? I've asked guys I work with, and gotten 1 explanation I could grasp, but think there's a whole lot more to it.

if 12 volts power is going to a 12 volt device (horn? lights?), what's the need?

or if this is getting to far off topic, I can get that, too!

 

[brushogger]

NEVER cut into the factory wiring harness to connect accessories. Always come off the battery with an accessory fuse block to build new circuits. Having to repair hay wired factory wiring sucks.


Sent from my iPhone using Tapatalk

 

[UK4X4]

Like most things there are a hundred ways of doing each one

Crimps- there are cheap chinese crap- and there are US or european versions from quality suppliers

Auto manufacturers use crimps cos its cheap and quick to assemble a loom with semi trained people


A good crimp is designed for the wire gauge and OD of the wire insulation- the crimp should both crimp the wire and the insulation

I'm sure we've all seen the crimp where the insulation does not even reach the crimp


Butt crimps with an overlay of heat shrink would be fine- the heat shrink holds the joint and does not allow for movement

Those blue wire splices are garbage for the pre mentioned reasons


In the photo you show un insulated crimps in a live circuit- on the back of the switch, theres 4 short circuits waiting to happen

Only use fully insulated crimps- or heat shrink over the top


Me- I did an industrial instrumentation apprenticeship back when wire wrap pins were still used on circuit boards and one of the reactors used a ferrite ring computer !

The soldering course took a week with us soldering "fishing nets' of wire and each solder checked under a microscope

I usally solder and heat shrink all wiring joints even on the back of switchs, I don't use a crimp

Probably the only place I don't solder is on relays as they are a replacement part- and can often fail

Its dificult to get but I usually use the glue filled heat shrink from 3M as it adds waterproofing and ridgity to the joint.


The issue with solder joints and vibration is as follows

in years gone by we had wires directly soldered to a board, so you had a flexible wire and a ridgid connection to the board, you could not sleeve the joint or support it

failure came through work hardenning of the wire as it entered the PCB or the pcb track lifted and broke on the board its self


These days most PCB's have a soldered socket and a plug- to get away from this issue


A heat shrink supported good soldered joint is supperior to a crimped conection in my book but both have homes in electrical vehicle wiring

Its more down to the quality of the equipment and the care taken to properly make up the connection.

Ie ratcheting crimpers rather than the 3dollar chinese crap
Good quality insulated crimps
the correct size and type of wire
The proper length strip
No cut little wires
Wire correctly positioned within the crimp so that the insulation is held too