Follow the symptom from thermostat to equipment
For Rosemont service, note whether the thermostat display is active, whether the fan runs and whether heating and cooling behave differently. This gives a clear starting point without requiring a homeowner to test live electrical components.
If the system works intermittently, record when it stops and whether the thermostat still calls. A repeatable description is more useful than replacing a thermostat solely because the room feels uncomfortable.
For indoor air quality, bring intermittent operation and controls into the scope discussion. Choose the measure that addresses the identified concern. Avoid a broad promise that an HVAC add-on will prevent illness or eliminate every indoor contaminant.
