In this month’s troubleshooting situation, we have a customer who has called to say that their condominium has no heat. The particular equipment in this case is a thru-the-wall package unit that provides cooling in the summer and employs a natural gas system to heat the building in the winter. The customer also informed the dispatcher that they had previous service on this equipment in the summer, and that the technician who responded to that request for service replaced the contactor. The unit operated normally through the rest of the cooling season, but failed to provide heat at the first start-up in the winter.
When you arrive and test cycle the unit by setting the thermostat to call for heat, you discover that the burners ignite, but after a delay, the system shuts down on the high limit switch due to the fact that the indoor blower motor did not operate.