Tech Tip: Diagnosing Voltage Drops

Voltage Drops in your Land Rover's Electrical System

When winter is coming, it's that time when all of your Land Rover and Range Rover's mildly irritating electrical quirks can turn into a full blown blizzard of trouble. Cold weather saps your battery's strength making the entire electrical system more prone to problems. One easy way to avoid electrical problems is to routinely use a meter to check your car's electrical systems.

The only tools needed to check the electrical system are a Digital Multi-Meter and some common sense. It is important to use a Digital meter since the old meters with a swinging needle are not sensitive enough to detect many voltage drops. It is equally important to read the information that comes with your meter and use common sense since a high voltage or current can quite possibly damage your meter.

A Voltage Drop is the amount of voltage a component is consuming from your car's electrical system. For example, a closed switch connected to a fully charged battery would have a Voltage Drop of .3 Volts or 300 milliVolts; the same switch would have a drop of 12.6 if it were open. If the switch is dirty or the connections corroded there would be a very noticeable Voltage Drop even with the switch fully closed. Such a Voltage Drop might make your lights dim or your starter turn too slowly to start your car.

You can use your Meter to check how fully charged your battery is, how good your ground wires are, your spark plug wires, your alternator or generator, your starter, your ignition coil, your, well, the possibilities are almost endless. A Meter can point up problems that a visual inspection will miss; that wire that looks great at each end might be corroded or even broken in the middle - a quick check with the Meter will tell you.

Everything in your car takes some electricity from the system (that's why you need a charging system to re-charge the battery). A long wire uses more than a short wire, a thin wire uses more than a fat one, a corroded wire uses more than a clean one. Typically Voltage Drops should not exceed the following:

place drop
Wire or Cable 200mV (.2V)
Switch 300mv
Ground 100mV
Connection 0 volts

Don't let cold weather and some overlooked electrical problems ruin your Rover fun. A little time under the hood with a good Multi-Meter will find problems before they find you.

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