No Heat / No Cool Troubleshooter
System suddenly stopped heating or cooling? Run these quick, safe checks first — many outages come down to a tripped breaker, a thermostat setting or a clogged filter. If these don’t fix it, call a licensed pro.
No Heat / No Cool Troubleshooter
Run these quick, safe checks before calling for emergency service — many outages are simple fixes.
Safety first: If you smell gas, leave the home immediately and call your gas utility or 911 from outside — do not touch switches. Never bypass a safety device or open sealed equipment.
AC running but not cooling
- Check the thermostat is set to COOL and the temperature is below room temp; replace the batteries.
- Replace a dirty air filter — a clogged filter is the #1 cause of weak or no airflow.
- Check your breaker panel: reset any tripped breaker for the AC / air handler.
- Look at the outdoor unit — is the fan spinning? Clear leaves or debris blocking it.
- Check for ice on the refrigerant lines or coil. If frozen, turn the system OFF and let it thaw.
- Make sure all supply vents are open and return grilles are not blocked.
Heat not working
- Check the thermostat is set to HEAT and above room temperature; replace the batteries.
- Replace a dirty air filter — restricted airflow can shut a furnace down on a safety limit.
- Check the breaker panel and, for gas furnaces, that the unit’s power switch is ON.
- Confirm the gas supply valve is open (gas furnaces) or the pilot/ignitor is working.
- Make sure the furnace door/panel is fully closed — a loose panel trips the safety switch.
- Check that vents and returns are open and unobstructed.
Still not working after these checks?
Find 24/7 emergency HVAC pros near you →This checklist covers common, homeowner-safe checks only. This tool provides a rough estimate for general informational purposes only and is not professional advice, a guarantee, or a quote. Results may not reflect your specific situation. Always confirm with a licensed HVAC professional before making any purchase or decision. See our Terms of Service for details.