Since a circuit must be complete to allow any electrical or electronic component to function, the troubleshooting process always begins with a circuit test.
The most basic test and most obvious test is to attempt to activate the system. If the load device (an electric fan motor, for instance) functions, the circuit is complete.
That, however, does not guarantee that the circuit is on good condition.
The possibility always exists that there are poor connections, high resistance, or leakage that would result in the load device receiving less power than intended.
When such problems become serious, the result will frequently take the form of a fan that turns too slowly or a light them is not as bright as it should be.
Two tools are commonly used to test circuits:
1. A Test Light.
2. A Volt/Ohm Meter (VOM).
A test Light can be used to verify that there is power at a given point in the circuit.
A VOM will give the actual voltage at the point in the circuit where the measurement is taken. A VOM can also be used to measure the resistance in a given wire or component.
The most common test routine is to perform a functional test of the system by turning it on and then systematically working back from the load device to the power source to identify the cause of any problems.
If there is power in the correct amount at the load device and it doesn't function, the problem lies within the device necessitating that it be repaired or replaced.
If there is no power, tests are conducted on each component in the circuit until the problem is found. Common problems include malfunctioning switches, poor grounds, and failed components such as resistors or capacitors.
Component tests are most frequently performed in one of two ways ways:
1. Using a Test Light/VOM connected to a good known ground and to successively to each terminal on the suspected component. Power in but no power out indicates that a problem exists in the component.
2. Using a jumper wire to bypass the component. If the jumper wire is connected across the component terminals and the load device begins to function the problem exists within the component.
There are two instances in which testing using a jumper wire across the terminals of a component can produce problems:
1. Tests shouldn't normally be performed across any resistors in the circuit since the since the purpose of the resistor is to reduce the current flow to the load device. Bypassing the resistor could damage the load device.
2. In the case of a load device that uses a large amount of power, any jumper wire must be heavy enough gage wire to supply the needed power. If the wire is too small, it will most likely overheat and under any circumstances will not carry the minimum amount of current required for normal operation.
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