For a furnace functioning correctly, what should the main gas valve terminals measure?

The main gas valve terminals in a gas furnace should measure 24 volts when the furnace is functioning correctly. This voltage is part of the low-voltage control circuit that operates the gas valve. When the thermostat calls for heat, it sends a signal that energizes the gas valve, allowing gas to flow into the burners.

The usage of 24 volts is standard in residential heating systems because it provides a safe operating level that minimizes the risk of electrical shock while effectively controlling the components of the heating system. Understanding this voltage is crucial for troubleshooting and ensuring that the furnace operates safely and efficiently.

Higher voltages, such as 120 or 48 volts, are not typical for gas valve operation in residential systems; they are more commonly associated with other electrical components, like the blower motor or general electrical supply systems. A measurement of 0 volts could indicate that there is no power reaching the gas valve, which would mean that the furnace cannot function properly.