To measure flame rectification in a gas furnace, a technician should check which of the following?

Measuring flame rectification in a gas furnace involves evaluating the small electrical current generated by the flame itself. When there is a flame present, it acts as a rectifier, allowing only direct current (DC) to flow through the system and indicating that combustion is occurring properly.

The technician should check for DC microamps because this measurement provides insight into the effectiveness of the flame in generating the required electrical current for the safety and operation of the furnace. A typical flame rectification current is very low, often measured in microamps, and is crucial for flame safety circuits in modern gas furnaces. If the microamp level is too low, it may indicate that the flame is not stable, or that there is a problem with the ignition system or burner operation.

Measuring AC volts, resistance, or continuity does not specifically address flame rectification. AC volts would pertain to the alternating current supply rather than the DC current needed from the flame, while resistance measurements deal with the components of the circuit rather than the active process of flame rectification. Continuity checks are used to verify that electrical connections are intact, but they do not provide information regarding the operational status of the flame or its ability to generate the necessary microamp signal for safe furnace operation.