Chapter Eleven -

Connectors and Terminals

Because all of the wiring in a house truck or bus is subjected to vibration and extremes in temperature and humidity, installing your wiring using the proper connectors is of the highest importance. Many of the circuits in use will be low voltage battery power, some with significantly high current flowing through the wiring. Keeping voltage drop to a minimum is essential, as is insuring that connections stay tight throughout the life of the installation. Use of connectors designed specifically for the job will make these goals easily attainable.

As we discussed last issue, the majority of wiring in your vehicle should be stranded-type wiring, which is very difficult to properly 'wrap around' screw terminals. For this reason, you will want to install 'ring' or 'spade' crimp-on terminals to make connection to screw-type fixtures. These terminals come in a variety of wire and stud sizes, and you should try to select the size that best fits both the wire and the screw/stud that you will be connecting it to. Specialised pliers are used to provide the 'crimp' that retains the wire and makes the connection. The successful installation of these terminals depends on use of the proper tool. Larger wire sizes may use 'crimp'-type connectors, or alternately, a pressure-type connector, with the pressure provided by some means of a screw device. Selection if the proper connector for the wire size is even more important with these type of connectors. Nearly all types of crimp connectors will benefit from the correct application of solder after crimping. This will lessen the resistance of the connection, minimising associated voltage drop.

Insulated crimp connectors, aren't very convenient to solder, so if you know you will be applying solder to your connections, use uninsulated terminals, and apply heat shrink tubing after soldering. This inexpensive tubing comes in a variety of sizes and colours, and can be written on with an indelible pen to identify wires. Installing crimp terminals on solid-type wire is always a loosing proposition. You will find that the connection will nearly never remain tight. Soldering these terminal in place is the only way to insure a tight connection. NOTE: Wires that are to be inserted in a pressure-type connector (or placed directly under a screw terminal) should NEVER be coated with solder before installation!!! Solder is a semi-solid liquid, and will 'relax' over time, leaving your connections loose and unreliable.

In general, you should avoid using twist-on wire connectors whenever possible, except, perhaps, in line-voltage AC wiring, and then only inside approved enclosures. While these 'wire nuts' are capable of making a secure connection, they do nothing to prevent intrusion by water, bugs and stray conductive objects, and they do not stand up well to stretching or abuse from flexing.

Connections made directly to battery terminals require special consideration. If your batteries have automotive-type round posts, use standard cables or cable ends to make your connection. Lead battery cable ends are pretty well acid proof, and are easiest to install and maintain. Screw post-type battery terminals are a bit trickier, as regular brass or tin-plated copper connectors are susceptible to corrosion and don't hold up well. Aluminum pressure-type connectors are also risky business here. The best bet is to use commercially available anti-corrosion terminal pads, and liberally coat any terminals on the batteries with an anti-corrosion coating. Crossing your fingers and cleaning the battery tops often won't hurt either! Any hardware you use here, such as washers, nuts, etc., should be made of stainless steel for best durability. Resist the temptation to place more than one wire in a connection before crimping or soldering it. Most likely, you will regret it later when the wires need to separated due to a wiring change. Crimp terminals are also difficult enough to align and neatly dress in a wiring loom, the more wire contained in a single connector, the harder it is to do an orderly job of it (and neatness counts!).