Before-you-call guide
Thermostat and system checks before you call
A few safe observations can help you describe the problem. Do not remove electrical panels, bypass safeties, handle refrigerant components or continue operating equipment with smoke, gas odor or electrical damage.
Check the thermostat mode
Confirm the thermostat is set to Heat or Cool as intended and that the setpoint calls for operation. If the display is blank, check whether it uses replaceable batteries.
Heat-pump thermostats may show Auxiliary Heat or Emergency Heat. Those modes have different purposes; note what the display says rather than repeatedly changing settings.
Check accessible power controls
If it is safe and familiar, confirm the normal equipment service switch and relevant breaker have not been turned off. A breaker that trips again should not be repeatedly reset.
Do not open equipment panels or touch wiring.
Look at the filter
A heavily loaded or incorrectly installed filter can restrict airflow. Note the filter size, condition and how long it has been installed.
Do not run the system without a filter unless a technician specifically directs you to do so.
Observe without disassembling
Listen for startup, blower and outdoor-unit operation. Note unusual sounds, odors, water, ice, error codes and whether air from registers changes.
Photos of thermostat messages, model plates and visible conditions can help when requested.
Know when to stop
Leave the building and contact the gas utility or emergency services for gas odor or a carbon-monoxide alarm. Use emergency services for smoke or fire. Shut equipment off if safe when there is sparking, electrical burning or significant water near electrical components.