Gas Heat ESCO Practice Exam

A customer complains that a 2-year old gas furnace will not light. The technician determines that the furnace locks out while attempting to light and reads 19 VAC at the gas valve. The technician concludes:

1. Transformer could be faulty

2. Gas valve is faulty

3. Thermostat needs recalibration

4. Ignitor is not working

The correct answer is: Transformer could be faulty

In this scenario, the technician's conclusion that the transformer could be faulty is the correct one. When the technician reads 19 VAC at the gas valve but the gas furnace still fails to light and locks out, it indicates that the voltage is reaching the gas valve, but there may not be enough voltage or current to actuate the valve properly. This could be due to a fault in the transformer that is not providing the correct voltage to operate the gas valve effectively. Therefore, it is essential to inspect and potentially replace the transformer to resolve the issue with the gas furnace not lighting. The other options are not as relevant in this situation: - The gas valve being faulty would typically result in no voltage reaching it at all, rather than the partial voltage described in the scenario. - If the thermostat needed recalibration, it would not cause the furnace to lock out while attempting to light. - If the ignitor was not working, there would usually be a lack of initial ignition, rather than the furnace locking out during the lighting process.