What contact tester and how to use?

I keep seeing warnings saying that using a non-contact voltage tester shouldn't be relied upon. I'm going to be replacing my bathroom fan; I want to test the wires both when they're free (are there 3 of them? - black, white, ground?) and when they're attached to the bathroom fan housing's outlet/plug receptacle. What do I buy for a contact test? And, when the wires are free and not connected to the fan's receptacle, what wires do I touch with the contact tester?

Thanks

 

Use a multimeter (analog) and test from your wires to either a known neutral or bare ground

 

A $8-$15 analog multimeter is a good choice. Cheap digital meters can be fooled by induced voltage and can give erratic readings if the battery is failing. An expensive digital multimeter may be more accurate but you don't need to waste your money when a cheap analog will do the job.

 

If you don't feel comfortable working with hot wires, by all means, don't do it. To test the wires the power would need to be turned on and the fan switch will also need to be turned on. Using the probes on the meter, check the black (hot) wire with one probe and the white (grounded neutral wire) with the other probe and you should get a reading of 120 volts. Then touch the hot wire with one probe and the ground wire with the other probe and you should also get a reading of 120 volts. If you touch the white wire and ground wires with the two probes you shouldn't get any voltage reading at all. Then, turn off the switch and the circuit breaker and wire the receptacle in the fan and reinstall the fan motor and fan wheel.

For a beginner, I think I'd recommend a solenoid type tester rather than a multimeter.

IDEAL INDUSTRIES, INC. - Solenoid Voltage Testers

 

Also you can buy alligator clips to slip on the ends of the probes so you can connect with the power off then turn the breaker on. Much slower testing but safer.

Nice thing about the solenoid testers (AKA Wiggie) is easy to use two handed. With a multimeter you almost need a third hand to hold the meter.