HVAC Not Working? Follow This Troubleshooting Guide

When your HVAC is not working, a systematic approach helps identify the problem. Follow this guide before calling for service.

Step 1: Check the Thermostat

Verify Settings - Correct mode (heat/cool/auto) - Temperature set appropriately - Fan setting (auto vs. on) - Not in vacation or hold mode

Check Power - Display working? - Batteries fresh (if applicable) - No error codes

Test Response - Change setting and listen for system response - Most systems respond within minutes

Step 2: Check Air Filter

Inspect Filter - Remove and examine - Hold to light - can you see through it? - Replace if dirty

Why This Matters - Dirty filter restricts airflow - Can cause system shutdown - Often the simplest fix

Step 3: Check Power Sources

Electrical Panel - Look for tripped breaker - HVAC may have multiple breakers - Reset once if tripped (if trips again, call pro)

Furnace Switch - Light switch near furnace - Easy to bump accidentally - Should be in ON position

Outdoor Disconnect - Box near outdoor unit - Should be closed/engaged - Check for damage

Step 4: Inspect Equipment

Indoor Unit - Listen for unusual sounds - Look for water leaks - Check for error codes/lights - Ensure panels are secure

Outdoor Unit - Fan spinning? - Any unusual sounds? - Debris blocking airflow? - Ice formation?

Step 5: Check Vents and Returns

Supply Vents - Open and unblocked? - Air flowing when system runs? - Temperature of air appropriate?

Return Air - Not blocked by furniture? - Filter area clear? - Good airflow?

Decision Points

System Runs But Does Not Heat/Cool - Check filter first - Verify thermostat settings - Give system 15-20 minutes - If still not working, call for service

System Does Not Turn On - Check all power sources - Check thermostat - If power okay and no response, call for service

System Short Cycles - Check filter - Check for blocked vents - May indicate refrigerant or sizing issue - Call for service if continues

Unusual Sounds or Smells - Burning smell: Turn off and call immediately - Grinding: Turn off and call - Other sounds: Note and schedule service

When to Call a Professional

Immediately - Gas smell - Burning smell - Carbon monoxide alarm - Electrical sparking

Soon - No heat when freezing - No cooling when extremely hot - System not responding to troubleshooting

Schedule Service - Performance issues - Unusual sounds - Efficiency concerns - Regular maintenance due