This month’s troubleshooting situation involves an air-to-air package unit heat pump that is approximately six years old, and the customer’s complaint is that, rather than providing cooling, it’s just blowing warm air.
When you arrive, you confirm that the thermostat is set in the cooling mode and the fan switch is set in the AUTO position, and that no cooling is taking place. Since the single return is nearby in the ceiling, you also check the filter, which the customer replaced before they called for service. The customer also confirms that they replace the filter every month.