Found this on the Web might be of interest...
Although I started the paragraph saying that I like them, there's a few rules to using these as well. Firstly, don't have any uncovered wire outside the crimp; make sure that you have only enough wire to make the connection safe. If the crimp hole is too large for the wire, then double the wire up to fill the hole. Use only the correct colour crimp for the job. These are:
Red for 0.50-1.5mmsq. Blue for 1.5-2.5mmsq. and Yellow for 4.0-6.0mmsq.
Then there is the cowboy's favourite way of connecting wires together and I' m sure you've all seen it as well; that is to twist the wires together and cover with either, sticky tape, plasters or, if you're really lucky, insulation tape - but not wrapped neatly either.
The way that I prefer to join wires together is with solder and heat shrink sleeving. There is of course a knack to doing this and I'll try to explain it clearly. Firstly you must unwrap the wiring harness far enough back to expose your wire sufficiently. This isn't always easy as you might be on your back underneath the dashboard but it has to be done. Then cut off the required length of shrink wrap sleeving to cover the joint - remembering that it has to go over two wires and, of course, the solder after the joint has been soldered. Then the clever bit: fit the shrink wrap onto the wire, remembering to keep it away from the heat of your iron, or else it will start to shrink before you can get it over the joint!
Remember that you must not have any solder spikes on your joint as these can break through the insulation after it has shrunk, causing it to short out with the next wire when you re-cover the loom with new insulation tape. If there is a need to join more than one wire into an existing loom then the only safe way is to cut the wire in the loom and join the new one with one of the two ends; get your shrink wrap over the biggest soldered end, then resolder the other end onto the joined wires and recover with the shrink wrap and introduce back into the loom. I have seen cases where the insulation has been stripped back a little bit on the wire and the new wire just wrapped around the open joint and then taped. This must not be done as it is very dangerous because it will be impossible to get a sufficiently tight joint to be electrically safe - and therefore can go high resistance and start a fire - especially if you are trying to introduce another live wire, say, for a radio memory or an amplifier.
The most common cause for blown fuses is badly fitted wires, through holes in the metalwork of the car, chafing the insulation and causing a short circuit. If you must go through the metalwork then you should fit a grommet so that your wire cannot chafe. Bad earths are also a reason why things won't work and it is very useful to have the correct tool to find these things. I use a device called a Power Probe. This is connected to the battery live and earth and has a switch on it to give either 12v+ or 12v-. It has a continuity function and tells you whether your wire is live or dead or earthed. When dealing with modern vehicles that have airbags, it is even more critical that, before cutting wires or joining wires to them, you ascertain whether or not they are part of the airbag circuit. There is nothing worse than having that go off in your face and it is very expensive to get them put back. If possible, always join extra lives to the appropriate wires in the fuse box. Very often there will be spares to join to. If there aren't any spares you can always join to the battery terminals themselves. There is a number of slave fuse boxes that you can buy nowadays and all you have to do with these is to find somewhere safe to fit them. Then connect one large, live cable from the battery "+" terminal, and simply use the outputs that you need, with the appropriate fuses.
Remember that you should always fit the correct fuse into the circuit if you are making a new one. Also, in the case of fitting car audio amplifiers, make sure that you not only use the correct size of wire for the electrical side but also for the speaker side. If wires have to go under carpets or through the sills then the same rules apply to make sure that they don't go over sharp bits of metal or through holes without grommets. I haven't mentioned, as yet, the advantages, or otherwise, of using insulation tape, so I'll do that now.
Insulation tape is worth its weight in gold in certain areas but is a right pain if used in the wrong areas. For example, to reinsulate a wiring loom after work on it, is good, and to cover new wires inside the car loom is good. But beware of fitting it inside the bonnet area as this is a hot spot for plastic wrapping and can cause it to harden and shrink and subsequently come off. There is also the problem of water entering the engine compartment. This, too, can cause the tape to come unstuck and, therefore, to come off. In cases where heat and water may be a problem, you can use either self amalgamating tape or split corrugated tubing that allows you to open it down the split to put the wires inside it thus protecting them. Then, as a rule, you put a bit of self amalgamating tape over each end to protect it and then use tie wraps to attach it somewhere safe away from excessive heat and abrasion from pulleys, belts, fans, etc.
I haven't mentioned yet the advantages of using tie wraps as, to my mind, they are the best thing to hit car wiring for a long time. They are neat, you can put them through holes and suspend cables where it wouldn't be possible before, or you can bunch up groups of cables neatly and carefull. I'm sure that you will have your own favourite uses for these things but they really do come into their own when doing work on cars.
Now I'll cover the art of wiring a socket for either a trailer or a caravan. I've seen so many bad ones that this information is essential.
It really isn't hard to do this type of job and, if you only follow the instructions on the socket pack and use the correct cable, (you can even get these pre-wired) then, as long as you connect them into the rear light loom to the correct wires, and re-insulate them afterwards, you can't go wrong. As previously mentioned, I have a power probe which enables me to put the pointed probe into the insulation and gently touch the wire inside without causing any real damage to the outer, other than a tiny little pin prick. By this method I can ascertain its electrical state, ie. live, dead or earth. This isn't quite as easy as it sounds as countless pin-pricks into my hand will show! I've also learnt to carry a box of plasters with me, as blood can stain car upholstery and is difficult to remove. To say that I have seen more cock-ups with this type of wiring would be underestimating the truth, but here is a few things to try to avoid:
Firstly, don't connect your new wiring directly to the rear of the bulb unit, as this not only looks messy but makes it difficult in some cases to change the bulbs when they blow.
Don't trap the wires under the spare wheel or jack, as I have seen this done more times than I can remember.
Don't leave the new wiring where it can get caught by items placed in the boot, or in a tray of water, as boots often accumulate water if the lids don't close properly. As you are probably guessing by now, this is another use for my old mate, the tie wrap, as experience has shown that there are always holes in the rear of the boot that (I would like to think) were made for this purpose. If there are no holes, you can buy a self-adhesive "saddle" with an "eye" for a cable tie.
There are several different things on the market to join wires together and I will take you through what and when to use them and when not to use them. Let us start with our old friend the "chocolate block" as we know it or "screw terminal connection block" to give it its proper title. I, personally, do not like to see these used in connection with car wiring for reasons that I will explain. Firstly they are very bulky and it's difficult to know if you have screwed them down loosely, or so tightly that you have severed most of the wires and the joint is only held by a strand. You could also trap the insulation underneath the screw and so don't make an electrical connection at all, or the screw head breaks when you are tightening it. Worst of all, the screw has been cross threaded from new and, when you tighten it fully, it doesn't touch the wire at all, leaving you then to wonder why the new unit that you have just installed won't work at all. resulting in countless hours of checking your own work.
Then there are the auto electrician's friend - the crimp connectors. These consist of Butt, Spade, Bullet, Piggy Back, Pin, Fork, Snap Lock, Flag, and closed end connectors. Some of these come with male and female variants. I must admit that I do use these, but not as much as I used to. These items are very safe, if used correctly, but you must have the proper tools to do the job correctly. Merely having cutters and pliers isn't good enough as, in my experience, there is no guarantee of consistent crimp connections being the same, ie . some of them are easy to crimp and some of them need a vice to crimp them. Therefore the only recommended way is with a double crimp ratchet type tool, not cheap but the only way to do the job properly.Although I started the paragraph saying that I like them, there's a few rules to using these as well. Firstly, don't have any uncovered wire outside the crimp; make sure that you have only enough wire to make the connection safe. If the crimp hole is too large for the wire, then double the wire up to fill the hole. Use only the correct colour crimp for the job. These are:
Red for 0.50-1.5mmsq. Blue for 1.5-2.5mmsq. and Yellow for 4.0-6.0mmsq.
Then there is the cowboy's favourite way of connecting wires together and I' m sure you've all seen it as well; that is to twist the wires together and cover with either, sticky tape, plasters or, if you're really lucky, insulation tape - but not wrapped neatly either.
The way that I prefer to join wires together is with solder and heat shrink sleeving. There is of course a knack to doing this and I'll try to explain it clearly. Firstly you must unwrap the wiring harness far enough back to expose your wire sufficiently. This isn't always easy as you might be on your back underneath the dashboard but it has to be done. Then cut off the required length of shrink wrap sleeving to cover the joint - remembering that it has to go over two wires and, of course, the solder after the joint has been soldered. Then the clever bit: fit the shrink wrap onto the wire, remembering to keep it away from the heat of your iron, or else it will start to shrink before you can get it over the joint!
Remember that you must not have any solder spikes on your joint as these can break through the insulation after it has shrunk, causing it to short out with the next wire when you re-cover the loom with new insulation tape. If there is a need to join more than one wire into an existing loom then the only safe way is to cut the wire in the loom and join the new one with one of the two ends; get your shrink wrap over the biggest soldered end, then resolder the other end onto the joined wires and recover with the shrink wrap and introduce back into the loom. I have seen cases where the insulation has been stripped back a little bit on the wire and the new wire just wrapped around the open joint and then taped. This must not be done as it is very dangerous because it will be impossible to get a sufficiently tight joint to be electrically safe - and therefore can go high resistance and start a fire - especially if you are trying to introduce another live wire, say, for a radio memory or an amplifier.
The most common cause for blown fuses is badly fitted wires, through holes in the metalwork of the car, chafing the insulation and causing a short circuit. If you must go through the metalwork then you should fit a grommet so that your wire cannot chafe. Bad earths are also a reason why things won't work and it is very useful to have the correct tool to find these things. I use a device called a Power Probe. This is connected to the battery live and earth and has a switch on it to give either 12v+ or 12v-. It has a continuity function and tells you whether your wire is live or dead or earthed. When dealing with modern vehicles that have airbags, it is even more critical that, before cutting wires or joining wires to them, you ascertain whether or not they are part of the airbag circuit. There is nothing worse than having that go off in your face and it is very expensive to get them put back. If possible, always join extra lives to the appropriate wires in the fuse box. Very often there will be spares to join to. If there aren't any spares you can always join to the battery terminals themselves. There is a number of slave fuse boxes that you can buy nowadays and all you have to do with these is to find somewhere safe to fit them. Then connect one large, live cable from the battery "+" terminal, and simply use the outputs that you need, with the appropriate fuses.
Remember that you should always fit the correct fuse into the circuit if you are making a new one. Also, in the case of fitting car audio amplifiers, make sure that you not only use the correct size of wire for the electrical side but also for the speaker side. If wires have to go under carpets or through the sills then the same rules apply to make sure that they don't go over sharp bits of metal or through holes without grommets. I haven't mentioned, as yet, the advantages, or otherwise, of using insulation tape, so I'll do that now.
Insulation tape is worth its weight in gold in certain areas but is a right pain if used in the wrong areas. For example, to reinsulate a wiring loom after work on it, is good, and to cover new wires inside the car loom is good. But beware of fitting it inside the bonnet area as this is a hot spot for plastic wrapping and can cause it to harden and shrink and subsequently come off. There is also the problem of water entering the engine compartment. This, too, can cause the tape to come unstuck and, therefore, to come off. In cases where heat and water may be a problem, you can use either self amalgamating tape or split corrugated tubing that allows you to open it down the split to put the wires inside it thus protecting them. Then, as a rule, you put a bit of self amalgamating tape over each end to protect it and then use tie wraps to attach it somewhere safe away from excessive heat and abrasion from pulleys, belts, fans, etc.
I haven't mentioned yet the advantages of using tie wraps as, to my mind, they are the best thing to hit car wiring for a long time. They are neat, you can put them through holes and suspend cables where it wouldn't be possible before, or you can bunch up groups of cables neatly and carefull. I'm sure that you will have your own favourite uses for these things but they really do come into their own when doing work on cars.
Now I'll cover the art of wiring a socket for either a trailer or a caravan. I've seen so many bad ones that this information is essential.
It really isn't hard to do this type of job and, if you only follow the instructions on the socket pack and use the correct cable, (you can even get these pre-wired) then, as long as you connect them into the rear light loom to the correct wires, and re-insulate them afterwards, you can't go wrong. As previously mentioned, I have a power probe which enables me to put the pointed probe into the insulation and gently touch the wire inside without causing any real damage to the outer, other than a tiny little pin prick. By this method I can ascertain its electrical state, ie. live, dead or earth. This isn't quite as easy as it sounds as countless pin-pricks into my hand will show! I've also learnt to carry a box of plasters with me, as blood can stain car upholstery and is difficult to remove. To say that I have seen more cock-ups with this type of wiring would be underestimating the truth, but here is a few things to try to avoid:
Firstly, don't connect your new wiring directly to the rear of the bulb unit, as this not only looks messy but makes it difficult in some cases to change the bulbs when they blow.
Don't trap the wires under the spare wheel or jack, as I have seen this done more times than I can remember.
Don't leave the new wiring where it can get caught by items placed in the boot, or in a tray of water, as boots often accumulate water if the lids don't close properly. As you are probably guessing by now, this is another use for my old mate, the tie wrap, as experience has shown that there are always holes in the rear of the boot that (I would like to think) were made for this purpose. If there are no holes, you can buy a self-adhesive "saddle" with an "eye" for a cable tie.
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