If an electrical appliance's performance begins fluctuating, resist the temptation to immediately replace the device. You may have a problem with the electrical socket not providing enough electrical current. There are several basic troubleshooting steps you can take to determine whether you have a problem with the appliance, the electrical socket or the entire circuit. Testing and troubleshooting your own electrical wiring can eliminate the need for a costly electrician visit. You can test your sockets and wiring with a multimeter and a voltage meter.
Power off the problem device and unplug it.
Plug a different AC device into the outlet and test it. If the second device also fails to work properly, you have a problem with your outlet.
Test the original device in a different outlet. If the device still does not function, you may have a problem with the circuit breaker or fuse attached to that circuit.
Move to the socket you suspect is defective. Touch one probe of the voltage tester to the contact on the "hot" side of the outlet. This is the smaller right-hand receptacle. Touch the other probe to the other side of the outlet, or "neutral." If voltage is present, the voltage tester bulb will light up or the buzzer will sound.
Use the multimeter for a second test of the outlet. Set the display of the meter to measure AC voltage, shown as a waveform on the dial. Attach the leads to the meter by their colour codes -- black for neutral or "COM," red for positive or "V+" -- and insert the leads into the outlet. Insert the leads into the outlet; with AC voltage, the orientation is irrelevant. Check the voltage reading, which should be approximately 110-120 AC volts for standard outlets in American homes. In other places, such as many European countries, the standard AC reading is 220-240 volts.
Set the multimeter's measurement to check for electrical resistance in ohms. Remove power to the circuit at the circuit breaker, and touch the leads to the contacts inside the outlet. If your resistance reads zero ohms, you have a short circuit. If it reads infinite resistance, the circuit is broken.
Dry your hands thoroughly before using any electrical tools or working near a live circuit. Also ensure that your testers and meters have dry and clean probes; otherwise, you could get a false reading or suffer electrical shock.