Vehicle Electrics Thread *PLACEHOLDER*

RIGHTY-HO!

Lets start with some electronics theory upside yo' head. I am only touching on the very very basics here to give a good impression of how electricity works in your car.

Electricity flows, like water. It follows the same physical principles as everything else. It wants to take the path of least resistance to get back to earth. Think of it as a pressured system (like central heating). It will flow from high pressure to low, always trying to equalise.

Electricity flow is electrons moving around. They move pretty slowly, actually. But one electron pushes on the next, which pushes the next, etc. Like a scaffold tube full of pingpong balls.

With that in mind, think of your car electrical system. The electricity is desperate to get from the positive terminal of your battery to the negative (a slight inaccuracy, it ACTUALLY flows from the negative to the positive, but this little "fib" of convention helps us understand and clarify things much more easily). A voltage is a potential, your car electrical system works at a potential of 12-14 volts. The negative terminal at your battery is at o volts. Note: That means that it is still a potential, it's just a potential of 0, it STILL counts as a voltage, this is important later.
Your battery is a big storage tank, full of electrons rammed in one side that want to escape to the other. The alternator rams more electrons in there, until it cant hold any more. Your battery has a capacity, say 60ah (amp hours), 90, whatever. Bigger battery, more amp hours, more electrons in there (again, this is not strictly true, but it will do for now).
When the electrons flow through something, they do something. Either give off light, heat, noise, whatever.

Keep that in mind as you work on your car. Electricity isn't magic. It's not something to be feared. It's just a tank of stored energy with a bunch of pipes coming off it. No different to your oil system, cooling system, fuel system...

So. Knowing that, we can come up with some safety tips:

SAFETY!

1) You wouldn't work on your engine while it was running unless you absolutely positively had to. So, lets not go poking around in the electrics while the battery is connected unless we absolutely have to. If you need to do something, disconnect the battery first.

Do this by taking off the GROUND terminal of your battery (if your car is positive earth, take of the positive terminal. If it's negative earth, take off the negative terminal. Typically, the earth will be the bug fat cable that is more like a braided strap than an insulated cable).

2) When you have to work live, be very very careful. Especially around your battery. Shorting out the live terminal of your battery to the chassis of the car will make a VERY big bang. Use insulated tools, have a fire extinguisher close to hand if you can, and use all your senses (touch, smell, taste, hearing and sight). If something smells acrid, gets hot, crackles or pops or bangs or flashes, then something is wrong.
Your battery, when shorted, may also boil. This will result in, at best, a pressure explosion of battery acid all over the place. At worst, your battery will give off hydrogen which really DOES go kaboom when there's a spark. Since you are playing with electric, there's going to be sparks. Best make sure you don't have any fuel leaks too while you are thinking about it

3) It's only 12v, but that does not mean it is not dangerous. Voltage is only half of the story, you need to think about amps too. Think of voltage as the pressure, and amps as the flow. You have a low pressure, VERY high flow system in your car. The biggest fuse you will find in your household appliances is 13A, your breakers are usually 30A. Your car electrical system can push hundreds if it has to. That creates a LOT of heat. And you don't have any breakers or RCDs in there to save you. Believe me, you CAN get hurt, so don't be blase about it.



There are many more safety tips, but we'll leave it there for now.

What tools are good to carry?

A good selection of tools in your retro or classic is essential if you want to get yourself out of trouble on the road. So, this is what I would recommend you put in your boot:

A cheapy digital multimeter
A spool of cable, something around 18awg for all-purpose getting-out-of-the-poo repairs
A pair of sharp snips
A pair of pliers
A small selection of screwdrivers (insulated for preference)
A handful of cable ties
A roll of electrical tape (all tapes are NOT equal. It's expensive, but I cannot recommend Scotch 88 tape highly enough. I used it all the time offshore, its durable, stretches well, doesn't unstick easily, and though they don't say it I can tell you from experience that if you apply it properly, its waterproof)
A cheap crimp terminal set
A handful of fuses
A spare relay
A bulb set
A stanley knife
A pair of wire strippers





So what is acceptable with connections and insulation?

Well, we see all sorts of things that make us wince with electrical systems, and lots of things we think look fine. You would be surprised what is, and isn't, ok!

Firstly, mains cable (as mentioned). It looks gash, it screams "BODGE!", but actually, it isn't. It's perfectly acceptable to use mains cable, or any cable, provided it is suitable for purpose.
So, the insulation must be in good order. The CSA of the cable must be suitable for the load it will carry, and for fault conditions it may be subjected to. Provided these considerations are met, there is no reason mains cable cannot be used, other than it looks gash as you like!


Connections... Frequently we see chock block, scotch block, electrical tape, crimps, and all manner of connections in a car. Lets start with what is NOT acceptable...

Insulation taped joints - these are an emergency repair ONLY! They should get you home and then be done properly! But if you are stuck, and need to do something to make a bodge to get you out of the poo, then the best way to make a joint is to strip around 20mm on insulation off. (Mine are a shade short here)



Put them together parallel, like this:



Twist them together



Tape them up like so



And make sure your tape goes over the end of the twists, like this:



If you have cable ties, stick one around the cables to hold them together and stop them coming apart when they get pulled. Make the repair good when you get home!!!!! Don't leave it like that!

So why do I suggest doing it this way? Well, you are getting the maximum contact between the cables, which means you aren't creating a weak point of less conductive material (dodgy connections create heat), you are getting a stronger bond than any other way, it will tolerate being tugged and pulled, and it looks gash as hell, which means it will be less likely to end up as a permanent repair!


Crimp Connections

I frequently see crimped connections that are not up to standard. So what is an acceptable way of doing it?
Well, a good ratchet crimp tool is essential. One like this:



Leave this one in your boot for emergencies:



How do you make a good crimp joint? What is good and what is bad? Well... Firstly, look at what you are crimping. If you have a flag terminal you need to put a spade onto, that will be different to if you are connecting two cables together. Use the appropriate crimp for the job! If your connection is carrying a live voltage (12v for example) then if is good practice to use an insulated crimp if possible, like this one:



If its going to be an earth, then insulation is not required.

Take your cable, and strip some insulation off the end (10 or 20mm). Be careful not to cut the conductors off too, if you do, strip some more off and try again! You can use cable strippers but I find a stanley knife of snips works for me too. Experiment, see what you feel best using.



So, you've stripped the cable. Pop the crimp on the end to check fitment. Trim your bared conductor if needed. The cable should be a snug fit inside the crimp, if its too loose, your crimp is too big. If its tight and there are strands sticking out everywhere, you are too small. DO NOT CHEAT! You cannot cut off strands to make it fit in and undersize crimp, if you do this, you are de-rating the capacity of the cable you are using. You are looking to make sure that the sheath of the crimp comes over the insulation of your cable, like this:



The conductor should hit the little stop in the crimp. You should NOT have any exposed conductor, like this:



Place it in the crimping tool:



And, squeeeeeeze! Keep going until the ratchet releases and the jaws open. Make sure your cable doesn't move while you are crimping, and thoroughly check afterwards both visually, and give it a good tug. You should not be able to physically pull it off the cable by hand.

a) Electrical problems are seldom the only problem!

4) The household connector blocks... You mean these?



They are just fine to use in theory, they are just ugly as sin, big, bulky, easy to over tighten and damage conductors and horrible in just about every way. As an aside, if you want a quick connector that is easy to use, reusable, neat, tidy and awesome in just about every way, wago connectors are wicked!

LOVE them!

Ah single core! Yes, that should not be used, ever, on a vehicle. Ever.

Different jaw sizes basically. There are a few different crimps and tools out there.

The issue with soldering is it doesn't cope well with being moved or vibrated, and as you say its easy to do but easy to get wrong.

Crimps are fine for repairs using bullet connectors though I tend to solder repairs and heat shrink them. I will post a "how to" later

Used to use those when I were a lad at a Peugeot dealers

106 and 306 air bag connectors underneath the front seats used to get the right hump with anyone weighing more than a string of onions in them. The official Peugeot fix was to cut out the connector and use Raychem joiners. And they knew how to charge for them too, 15quid for 3 in a pack

don't know how much I would trust something that can melt under a heat gun to hold a wire together in a car. Especially when solder and heat shrink is very easy and cheap.

The main problem with connector blocks is people use the wrong size (too big) and overtighten them, cracking the bottom of the casting. Either use the right size or double the cable over so it fills the connector. That saying, ive always used crimps for years as superior, and wago's where i can (i.e when stocked on company account).
And don't be tempted by what another lad on here did and explain how its far superior to not strip the cable and let the screw of the connector bite down through the insulation. Thats what leads to poor, high resistance joints.

(This info is not aimed at you btw fad, i gather that you know what your doing. What do you actually do job wise to have the knowledge youve displayed on electrics before? You seem a bit more involved than a normal sparky...)