Tell If a Thermocouple Is Bad
A thermocouple is a fail-safe element that ensures that gas doesn't flow when a pilot light is out. Thermocouples sense high temperatures when the pilot is lit. If the temperature is too low, it will not signal the gas flow to the burner. When that happens the water heater or other appliance will not work.
Instructions
1. Locate the temperature control knob on the lower face of the water heater. A small metal block protruding from the water heater body holds the temperature dial, the thermostat, the gas control knob, the pilot igniter button, the thermocouple connector and two gas line connectors.
2. Check the gas flow valve lever on the copper tube leading to the metal block with the temperature dial. The lever will be plainly marked with arrows showing which direction to turn it for "off" and "on." Pull the lever to "on" to be sure gas flowing to the unit.
3. Light the pilot light, if possible. Turn the gas knob to "pilot," push it in and hold it while pressing the igniter button. Look through the small pilot window to watch the igniter spark and light the pilot. Keep the gas knob depressed for 60 seconds after the pilot lights. If it refuses to light, the problem lies in the gas flow. If it goes out immediately when the knob is released, then the thermocouple is probably bad. Allow several minutes for the thermocouple to heat up if the pilot stays lit. If the water heater burner comes on, the pilot had simply blown out. Test the thermocouple if the pilot stays lit but the burner does not start within five minutes.
4. Turn the gas control knob and the gas flow lever to "off." Allow 30 minutes for the unit to cool.
5. Locate the thermocouple connector nut at the thermostat. The nut has a pliable copper wire extending from it. Loosen the swivel connector nut with an adjustable wrench, turning counterclockwise and pulling it slightly away from the thermostat. Certain Whirlpool models have nuts that loosen with clockwise turns.
6. Remove the burner access panel. Use a screwdriver to remove any holding screws or to release the clip holding the panel. Leave the cylindrical body of the thermocouple in place where it mounts near the pilot light.
7. Set a digital multimeter to read "amps." Clip the red hot lead onto the copper cylinder of the thermocouple. Clip the black lead onto the silver threads of the swivel nut that was removed from the thermostat.
8. Turn the gas flow lever and control knob to "on," light the pilot and watch the readings on the amp meter. The voltage will display at least 12 milliamps within one minute if the thermocouple is good. Replace the thermocouple if the meter shows less than 12 milliamps.
Tags: control knob, water heater, pilot light, flow lever, from thermostat, igniter button
