An electric burner may remain on high heat regardless of the setting on the burner control switch or it may not turn on at all. These are symptoms of a defective burner control switch.
This test is for an infinite, two-wire, burner control switch on an electric stove. Three-wire controls cannot be tested using this procedure. Testing of burner controls requires the use of a multimeter. Use of leads with alligator clips is helpful for ease of testing.
Before testing the burner control switch,
unplug the appliance or shut off the power at the fuse
box or breaker panel to avoid an electrical shock hazard.
Start by turning off power at the circuit breaker or by unplugging the appliance.
Remove the control panel back. It may be fastened with several small screws. Some controls may be accessed by lifting the entire stove surface with access being underneath. Controls at the front of the appliance may be secured at the far left and right sides or underneath with the oven door opened.
Locate the suspect switch for testing. Label all wires and terminals before disconnecting. A close up digital photo may be helpful.
On the burner control switch the terminal labeled "P" leads to the burner indicator light. The terminals labeled "H1" and "H2" lead to the burner element and the terminals labeled "L1" and "L2" (sometimes "N1" and "N2") are the power supply wires.
Set your multimeter to ohms setting x1. Turn the burner control to the highest temperature setting. Place one probe on pin "L1" and the second probe on pin "H1". The resistance measurement should be very low, zero to twenty ohms. If the test shows high or infinite resistance, the burner switch is defective.
Repeat the step above for the terminals "L2" and "H2".
If the control passes that test, turn the temperature setting to about the middle of the range and repeat the previous two steps. This will test for an intermittent problem with the switch. If the test does not show continuity with very low resistance, the switch should be replaced.
With the switch turned to the "Off" position, the resistance on each of the pairs of terminals tested above should now show no continuity or a reading of infinite resistance.
A test for continuity between "P" and "L1" when the burner control switch is on should show continuity. The light should be on whenever the control is turned on. If your test shows continuity, but the light does not operate, it is likely the bulb has failed.
If the burner switch shows high or infinite resistance, the switch is not passing along current to the burner and so the switch should be replaced.