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The Electrical system on a series 3 is a pretty straight forward set up. However when faced with a jungle of wires, various connectors and switches it can all seem pretty confusing. Add in terms such as voltage, amps, watts, resistance and ohms and its enough to make you give up from the start. If you own a Series 3 then at some point you are bound to come across a situation where you will need to fix some sort of Electrical issue. I’m no Auto Electrician but I will try and give you a few pointers to get you started so that armed with a few basic tools you should be able to confidently tackle a problem should it arise.
As a Series 3 is getting on in years is likely that corrosion is evident around the vehicle and the Electrical system is no exception.
A lot of issues concerning dim lights, indicators not flashing as they should, the starter motor not turning over quickly etc could be simply down to a poor earth or connection. Corrosion takes places on exposed wires and connections and reduces the effectiveness of the joint thus reducing the correct flow of electricity. The series 3 is negatively earthed, this means that out of the two terminals on the battery the one marked with a ‘-’ is connected to the chassis. The other terminal marked with a ‘+’ is used to feed all the electrical components either directly or via a system of switches. The chassis of the vehicle therefore is used to carry current and complete an electrical circuit.
BULB / LOAD
A SIMPLE CIRCUIT
BULB / LOAD
The diagram above shows a simple circuit needed in order for the bulb to work. When the switch is closed the circuit is complete and the bulb lights.
The diagram to the left shows a circuit with the metal chassis forming part of the circuit. In addition there is a fuse which is a safety link in the circuit to limit the amount of flow or ‘Amps’. If for some reason too much flow is introduced to the circuit the fuse will overheat, burn through and break the circuit. This diagram forms the basis of the electrical system in a series 3 Land Rover.