Troubleshooting tips for a thermocouple include using a multimeter instead of an ohmmeter, switching off power to the equipment being tested, and adjusting the multimeter correctly to take the appropriate readings. Also, bring the tester's probe and a terminal of the thermocouple in contact to take the readings.
A multimeter can read both voltage and resistance of a thermocouple. On the other hand, an ohmmeter can only read the resistance. Testing the thermocouple's resistance indicates if the device has a short.
Before troubleshooting a thermocouple, switch off power to the equipment to eliminate risk of an electrical shock from terminals and bare wires. Thermocouples have very low voltages, but the presence of other electrical components around it poses the risk of a shock.
When reading the thermocouple's resistance or voltage, position the wire leads in the appropriate labeled ports of the multimeter. Turn the meter's dial to the lowest resistance or voltage reading indicated, and touch any one thermocouple terminal with the meter's probe.
If the thermocouple is functional, the resistance reading should range from zero to extremely low. Higher readings indicate a dysfunctional thermocouple.
To read the voltage, after bringing a thermocouple terminal in contact with the meter's probe, place a hand on the thermocouple's end. If the voltage reading is zero, it indicates that the thermocouple is dysfunctional and requires replacement.