How to Test a Heater With a Multimeter

Turn off and unplug the heater.

Unscrew and remove the panel housing the power cord. Unplug the other end of the power cord from the base of the heating element.

Set the multimeter to continuity testing mode. Touch the positive lead to one of the two flat prongs on the heater's power cord. Touch the base of the cord with the negative lead. The multimeter will beep if the cord properly conducts electricity.

Touch the other flat prong with the positive lead. Touch the base of the cord with the negative lead. Listen for a beep. If the multimeter does not beep when testing both angled prongs, your heater's power cord is not properly conducting electricity.

Calculate the heater's resistance using the following equation where R is “resistance,” V is “voltage” and P is power in wattage: R=(VxV)/P. For example, a 120 volt, 1100 watt space heater would have a resistance of 13.09 Ohms.

Set the multimeter to measure resistance.

Touch the positive lead on the multimeter to the positive terminal on the heater's heating element. Touch the negative lead on the multimeter to the negative terminal on the heater's heating element. On most multimeters, the positive lead is red and the negative lead is black, although this may vary depending on the model. The multimeter will then measure the resistance of the heating element and provide you with an Ohms reading on the screen. If you do not receive an Ohms reading or the Ohms reading is significantly below what the heater's resistance should be, you need to replace the heating element.