How Do You Test a Triac?

Triacs can be tested with the use of a multimeter. A more advanced way of testing a triac is to perform a circuit test.

Triacs are three-terminal semiconductor devices used for controlling current. Their bidirectional construction means that current can flow through them in either direction. An acronym for Triode Alternating Current, Triacs are commonly used with AC switching applications. Common examples include small motor controls, dimmer switches and the speed controls on an electric fan.

The three terminals of a triode are commonly described as Terminal 1, Terminal 2 and the gate; T1 and T2 serve as the major current-carrying terminals, while the gate serves as a trigger.

Owners can test the health of a triac by following a few quick steps:

  1. Unplug the circuit and discharge the high capacitor.
  2. Set the multimeter to high resistance mode, which should be capable of reading up to 50 ohms.
  3. Connect the positive and negative leads to the triac's T1 and T2 terminals.
  4. Check the multimeter reading. It should indicate high resistance
  5. Repeat the process, this time setting the multimeter to low resistance mode.
  6. Check the gauge for a low resistance reading, which indicates that the switch is on. If present, then the triac is in good health. An abnormal reading would suggest otherwise