In this month’s troubleshooting situation, a customer has called for service, reporting that their heating system isn’t working. The equipment is a rooftop gas pack, and when you arrive you confirm the following:

1. The equipment power supply is correct.
2. All over-temperature protective devices are closed.

When you initiate a call for heat, you note that the combustion blower motor starts and operates properly, and that, after the appropriate delay, the direct ignition system operates, but the burner does not ignite.

As your next step, you disconnect the power supply, remove the wiring connections from the gas valve, and perform a resistance check on the coil. (See photo above).