HVAC Troubleshooting Center
Diagnose and fix common HVAC problems with our comprehensive troubleshooting guides
Emergency Situations - Act Immediately
Gas Smell
EMERGENCYLeave immediately, call gas company from outside
Electrical Burning Smell
URGENTTurn off system at breaker, call technician immediately
Carbon Monoxide Alarm
EMERGENCYEvacuate, call 911, do not re-enter
Major Water Leak
URGENTTurn off system and water, call technician
Quick Diagnostic Tools
Troubleshooting by Problem Type
Cooling Problems
AC not cooling, freezing, or cycling issues
AC Not Cooling
Common Symptoms:
- •Warm air from vents
- •No temperature change
- •Running but not cooling
AC Short Cycling
Common Symptoms:
- •Frequent on/off
- •Never reaches temperature
- •High bills
AC Won't Turn On
Common Symptoms:
- •No response
- •No fan operation
- •Dead system
Heating Problems
Furnace and heat pump heating issues
Furnace Short Cycling
Common Symptoms:
- •Frequent on/off
- •Overheating
- •Poor heating
Heat Pump Not Heating
Common Symptoms:
- •Cool air in heat mode
- •Constantly running
- •Ice buildup
Noise Problems
Unusual sounds from HVAC equipment
Banging or Clanking
Common Symptoms:
- •Loud bangs
- •Metal sounds
- •Startup noises
Squealing or Screeching
Common Symptoms:
- •High-pitched sounds
- •Belt noise
- •Bearing sounds
Clicking or Ticking
Common Symptoms:
- •Repetitive clicks
- •Relay sounds
- •Ignition clicking
Humming or Buzzing
Common Symptoms:
- •Constant hum
- •Electrical buzz
- •Vibration sounds
Water & Moisture Issues
Leaks, condensation, and drainage problems
AC Water Leak
Common Symptoms:
- •Water around unit
- •Ceiling stains
- •Pooling water
High Indoor Humidity
Common Symptoms:
- •Muggy feeling
- •Condensation
- •Mold growth
Furnace Leaking Water
Common Symptoms:
- •Puddles near furnace
- •Rust spots
- •Water damage
Frozen Condensate Line
Common Symptoms:
- •No heat
- •Error codes
- •Gurgling sounds
Electrical & Control Issues
Power, thermostat, and control problems
Thermostat Not Working
Common Symptoms:
- •Blank screen
- •Wrong temperature
- •No response
Frequent Breaker Trips
Common Symptoms:
- •Power loss
- •Repeated trips
- •Electrical smell
System Won't Turn Off
Common Symptoms:
- •Constant running
- •Won't cycle off
- •Frozen thermostat
Intermittent Operation
Common Symptoms:
- •Random shutoffs
- •Sporadic operation
- •Inconsistent cooling
Airflow Problems
Poor airflow, pressure, and ventilation issues
Weak Airflow
Common Symptoms:
- •Low air pressure
- •Poor circulation
- •Slow cooling
Hot/Cold Spots
Common Symptoms:
- •Uneven temperatures
- •Room differences
- •Comfort issues
Dusty or Smelly Air
Common Symptoms:
- •Dust from vents
- •Musty odor
- •Poor air quality
Most Common HVAC Problems
Top AC Problems
- 1. Dirty filter35%
- 2. Refrigerant issues22%
- 3. Capacitor failure18%
- 4. Thermostat problems15%
- 5. Drainage clogs10%
Top Heating Problems
- 1. Ignition issues28%
- 2. Dirty filter25%
- 3. Thermostat malfunction20%
- 4. Pilot light problems15%
- 5. Blower issues12%
DIY Fix Success Rate
- Filter replacement95%
- Thermostat issues75%
- Breaker/power60%
- Drainage clogs50%
- Refrigerant issues0% (Pro only)
When to Call a Professional
Try DIY First:
- ✓Filter replacements and cleaning
- ✓Thermostat troubleshooting
- ✓Circuit breaker resets
- ✓Basic drainage clearing
- ✓Simple pilot light relighting
Call a Pro Immediately:
- ✗Gas leaks or gas smell
- ✗Electrical burning smell
- ✗Refrigerant handling
- ✗Heat exchanger issues
- ✗Major electrical repairs
Can't Find Your Problem?
Use our comprehensive diagnostic guide or get expert help