Wiring do's and don'ts: A guide

[skishop69]

Since everyone likes to do their own work and mods, and electrical is one of those things that everyone thinks they know how to do, I thought I'd post this and hopefully save some people some frustration and headaches at the very least and disaster in a worse case scenario.

Chose the right wire:

Say you've got your garden hose out and you hook it to the fire hydrant and turn it on. BOOM! It blows out. Current is essentially electrical "pressure". Choose a wire with too small of a gauge and you will overheat it and melt it or worse. You certainly wouldn't use a 22 gauge wire for a 20 amp circuit. If you don't know what gauges are adequate for what loads, a quick Google search of wire gauges vs electrical loads will point you in the right direction. NEVER, never, never, did I mention never?, use solid copper wire in an automotive application. Bad monkey! No banana! Avoid any wire that will hold any shape you form it into. Stiff wires are not designed for automotive applications and tend to break over time due to the various vibrations inherent in a car. Finer strands of wire braided together inside the insulation are the preferred choice especially for data lines, wheel speed sensors or anything that sends a digital or AC signal.

Adding circuits:

If you need to add an accessory, don't just go in and tap an existing circuit without first knowing everything it powers, the gauge of the
wire and the size of the fuse protecting it. These circuits are designed for the specific current load they are supplying and adding to them can
overload them resulting in meltdown. If you are removing something and putting something else in it's place, that's ok as long as the something you're putting in draws the same or less current. You can't tap your running light circuit to add off road lights.  *See the above hose reference. When you add a circuit for power, always, always, ALWAYS add a fuse to the circuit as close to the power source as possible. This has been a source of contention in the past. There are those who believe it's not necessary and that belief is misguided. The federal government (which really tends to overdo things) has strict regulations for auto manufacturers regarding circuit protection. Every circuit in every car built since the mid 60's is fused one way or another. The two exceptions (in the past) were battery to starter and battery to fuse block. This is no longer true since the development of reliable high current fuse.

Fuses:

Fuses are there and the rating they are, for a reason. Protection of the device and the circuit, though more for the circuit in automotive applications. Protection from shorting, overload, overheating and possible fire. If it calls for a 15 amp fuse, use a 15 amp fuse. If a fuse keeps blowing, it's because there's a problem with the device or the circuit. This DOES NOT mean keep throwing a bigger fuse in it! No banana! This brilliant line of reasoning will cost you. Maybe just some repairs, perhaps your car, or maybe someones life. One experience with a Cadillac comes to mind. The owner thought it was ok to keep jamming a 30 amp fuse in a 15 amp location even though it kept blowing intermittently. Thankfully the car quit running all together and he had to have it checked. The job ended up taking 22 hours as I had to completely gut the interior of the vehicle and trunk to find all of the damage done to the wiring from the original issue that was by the E-brake pedal which I initially found in about 30 minutes. The continued installation of the bigger fuse allowed the circuit to overheat multiple times, melting the insulation on it and adjacent wires which then shorted out and overheated and so on. Due to the excessive damage, I ended up having to replace the dash harness, body harness, dash and body fuse blocks and the rear body harness. Total damages for said repeated offense: $8000+ and some change. How about that 15 amp fuse now? Circuit breakers can be used, but are not recommended. They are usually found in power window and power seat circuits since electric motors have what is known as rush in current. This higher draw of power is normal and can happen on startup or if the device binds up or is overloaded for another reason, so a CB is installed instead of a fuse allowing it to reset so use of the device can continue.

Splices:

When tapping into or repairing a circuit or extending a wire, the best method is solder and shrink tube. Lead free, rosin core solder and shrink tube with an imbedded glue. When heated, the glue will melt out and provide an airtight seal. Why an airtight seal? I'm glad I asked. I'll get to that in a moment. When tapping a circuit for an add on, cut the wire completely and strip both ends about 1/4". Strip the end of your new wire the same. Cut a piece of shrink tube at least twice as long as your stripped section. IE: 1/2". Slide it on to that section well away from the bare wire to avoid the heat from soldering. Twist your new wire to one side of the original wire you cut. Take that and twist it horizontally (both wires flat and pointing at each other) to the other half of the circuit you cut. When done correctly, it will look like a continuous wire, 'spiral' wrapped together. They also make bare metal crimps to join the wires. Now apply solder to the joined section. Let it cool. Slide the shrink wrap over the solder joint and position evenly on both sides of the joint. Heat and shrink.

The second best method is shrink type butt connectors. These type connectors are semi transparent and come in pink, light blue and yellow, each color for a specific gauge wire. DO NOT use plain Jane butt connectors unless you live in Arizona, Utah or Nevada. They do not seal and will let in moisture. Moisture and copper do not play well together and the copper will corrode over time causing a poor connection with high resistance leading to possible heat damage/melting, or to the point where the wire will actually break. Shrink type butt connectors have imbedded glue. When heated, the outter sleeves of the connector shrink and the glue melts sealing the connection. See above airtight seal reference.

Twisting and taping. This should only be used as a temporary, last ditch, emergency repair. It provides the least effective and weakest connection. Add to that, the majority of electrical tape people buy is cheap crap that will only stick for about a year or so before it starts to fall off. Then you get the fun of shorts, blown fuses, melted wires and if it's a really fun time, fire! Break out the marshmallows!

I saved the worst for last. Splice locks. These are the nifty, Satan invented devices that you lay your original circuit in along with your new wire and mash it all together with pliers. Seems like a quick, easy way to join wire, right? WRONG! These hellish little devices will actually cut wire strands in the bundle of wires you are joining, reducing their ability to properly conduct the current, leading to premature component failure and wire overheating. Please, please, please do not use these. See the first paragraph of splices.

The above information is for instruction purposes and is not my opinion, but an industry wide standard on how things should be done correctly. I have provided it to give you better ways to add and repair electrical connections. I did not post it to listen to, "Well my dad always did it this way" or, "My teacher said to do it that way." If they did, they are wrong. It may be they were uninformed or ill informed. Whatever the case, they are still wrong. I've been wrong many times. You get over it. In the immortal words of Irwin M. Fletcher, "It takes a big man to admit when he's wrong. I am NOT a big man." lol

If you have questions, or I've overlooked something, you know how to find me.
 

[AdventureSubaru]

Great write up!

[rdweninger]

What can I say ...  The guy knows what he's talking about.

  Next time you drive down the freeway, pay attention to the shoulder pavement.   You will see occassional areas that are blackened.  This is where a car was on fire.  Fire Bad.

[Numbchux]

Excellent write-up.


I have to disagree with this sentence, though.

 

 

When tapping into or repairing a circuit or extending a wire, the best method is solder and shrink tube

 

 

A solder joint is completely inflexible, and requires a pretty extreme heat cycle to the copper wire. These 2 factors can cause fatigue over time and I have seen them break (yes, even under good heat shrink). It's admittedly rare, and still better than a standard crimp connection or the others, but still enough of a concern that I don't use it.

 

I ONLY use Molex PermaSeal connectors, I buy them in bulk through Waytek Wire (they are available as spade and ring terminals, too):

https://www.waytekwire.com/item/30980/Molex-19164-0013-Perma-Seal-Butt-Connector-/

https://www.waytekwire.com/item/31980/Molex-19164-0044-Perma-Seal-Butt-Connector-/

https://www.waytekwire.com/item/32980/Molex-19164-0056-Perma-Seal-Butt-Connector-/

 

Obviously the process of heat shrink applies much less heat to the copper wire, and the semi-flexible nature of the heat shrink sleeve helps disperse the bending/vibration force through a slightly larger piece of the wire.

 

 

 

Also, you didn't address the other "option".....wire nuts. Wire nuts work for household wiring because households do not vibrate constantly, also because there is no vibration/movement, household wiring is solid-core, not multi stranded like automotive wire. These 2 differences mean wire nuts will fall off, and then you have a completely un-insulated connection.

[skishop69]

I agree, it can fracture, but it is actually far less common than wire fractures using the butt splices. What you listed is exactly what I was referring to. Heat cycling to the wire can be a factor, but if you are using the correct temp and tip, it really isn't an issue. It does take practice to get right and if you don't want to practice, or aren't confident in your soldering skills, the shrink butts work just fine. Like I said, this is just industry standard best to worst. Done correctly, the shrink butts are a very close second to soldering. I do use them on occasion, I just prefer the guaranteed connection of soldering. Thanks for the input guys!

 

Edit: Yeah, missed the nuts. NEVER, never, never, use wire nuts! Oy vey! lol

Edited August 3, 2016 by skishop69

[l75eya]

That was beautiful.

[MR_Loyale]

I would add that watch that your wire runs aren't up against any sharp objects. I got a Loyale used and the previous owner had installed new speakers in the doors by smashing the existing ones and putting new ones on top and using pointy wood screws to hold them in.

 

Whe I got it, the power door lock fuse would keep blowing. Turns out those pointed wood screw were poking into the wire over time.

Edited August 4, 2016 by MR_Loyale

[3crows]

I would take issue with this. "and electrical is one of those things that everyone thinks they know how to do". I hate electrical stuff! It has no moving parts that you can see and it WILL bite you! when you least expect it!

[damnsubaru]

don't forget the preinstalled smoke.

[skishop69]

We call that magic smoke. If you let it out, that unit no worky anymore. lol

[jsyme]

Bad monkey! No banana!

 

Too funny