How do you test to identify a bad resistor?

Answer 1

First you need to know the value of the resistor. Follow the link for a handy resistor calculator

After determining the value of your resistor simply test the resistor with an ohmmeter to see if it is at true value. General use should be within + or - 5%

Answer 2

Multi-meters have different measurement modes for measuring various electrical parameters. For resistance measurement for a resistor you need to ensure that it is in resistance measurement mode and leads are in the resistance/voltage measurement slots and not in the current measurement. There are auto range multi-meters and there are the ones in which range need to be adjusted manually. It also depends on why, how and what exactly is the purpose of the measurement. A resistor outside of a board or mounted on a board. While measurement, the hardware is powered up or not. If you need to measure exact value of resistance or just want to see if it is open or short.

Answer 3

A resistor is tested with a multimeter, set to the ohm scale, if the reading correspond with the markings on the resistor +- the percentage marking then the resistor is good although it can be faulty under load, in that case the an in circuit test can be perform by measuring the voltage drop across the resistor and then using Ohm law determining the correct reading. If the colour of the resistor is darker in the centre than the rest of the body, replace it.