Safety First |
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Electrical tinkering Whenever you are starting any kind of electrical work on your bus (replacing or repairing wiring, adding fog-lights, switches etc.) you must make sure you are not going to create sparks and lots of white smoke. At the very least they will cause you a lot of unnecessary extra work but it may be worse. You could do serious harm to yourself and/or the bus if you do not take some precautions. So, before you start, take a few moments and disconnect the battery. Note: If you have more than one, you will probably have to disconnect them all. The correct procedure is to disconnect the ground (negative) terminal from the battery. This will make it safe for you to work on the electrics without inadvertently causing a short circuit which could immediately burn out your wiring (or worse). This may sound strange to you. Why disconnect ground? Wouldn't it be more logical to disconnect the voltage carrying (positive) terminal from the battery? Well, there is a good reason. First: electrically speaking it does not matter which terminal you disconnect. When the circuit is broken no current can flow. It does not matter whether the circuit is open at the positive or at the negative terminal. BUT ... When you loosen the bolt or nut at the positive terminal of the battery you will need to use a spanner. When turning the (steel) spanner it may easily touch a metal part of the car body. That will create a massive short circuit! In fact you have now turned the battery and spanner into an arc-welding set-up with all the associated fireworks. I would strongly advise you not to try this. However when you first loosen the clamp on the ground terminal you can have the spanner touch the body of the car without any ill effect. The only thing to look out for is that it does not touch the positive terminal of the battery. With the ground clamp disconnected you can just leave the wire dangling somewhere away from the battery and you are entirely safe. There is even no need to disconnect the positive terminal. Of course, now that you are at it, this is a good moment to clean the battery terminals and add a little distilled water if your battery needs it. That will ensure longer trouble free use of your fairly expensive battery. Procedure for reconnecting the battery. When you're done with your work you can reconnect the ground wire to the battery. If you've done your work properly there won't be any problem. But if you're not sure use your multi-meter (you have one don't you?) to check for short circuits before you reconnect the battery. Make sure you have the battery installed the right way around (positive terminal near insulated cable, negative terminal near blank ground cable). First connect the clamp on the positive terminal. Leave the ground cable off until you are done with the clamp on the postive terminal. This ensures, for the same reason as above, that you will not have any mishaps. After the positive terminal is reconnected you could use you meter to check for short circuits by connecting it in between the ground cable and the negative terminal of the battery (electrical engineers call this an 'in series' connection). With everything in your bus switched off there should be no current flowing. Then you could open a door so the interior light comes on. This should give you a reading of a few hundred milliamps. It is best to use a digital multi-meter. These don't care about polarity so it does not matter which wire you connect to plus or minus). Set the meter to the highest current setting (most likely 10 Amps) when performing this test. You may have to insert the red test-wire into the high-current (10 Amp) socket on the meter. Keep spare fuses for your meter handy. Measuring high currents can easily result in blowing the fuse in the meter when there's something wrong in your bus. Remember a car battery can crank out several hundreds of amps. These can create big fat sparks and melt thick wires. Add a little gasoline and you could turn your bus into a nice bonfire. That's probably not your idea of having fun. Take care ... |
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Translation table for bus-owners across the pond:
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