Identify the exact symptom
Is it no heat, no cool, weak airflow, strange noise, bad smell, or short cycling? Pinpointing the problem saves time.
Read moreCheck the thermostat display
Is it blank, flashing, or showing an error code? A dead thermostat is the #1 false alarm for HVAC failure.
Read moreInspect the circuit breaker
Flip the HVAC breaker off, wait 30 seconds, flip back on. A tripped breaker is a quick fix that mimics a dead system.
Read moreCheck the air filter
A clogged filter causes 80% of HVAC service calls. Pull it out and hold it up to light — if you can't see through it, replace it.
Read moreVerify all vents are open
Walk the house and confirm every supply and return vent is open and unblocked by furniture, rugs, or curtains.
Read moreReplace thermostat batteries
Most thermostats use AA or AAA batteries. Dead batteries cause blank screens and lost schedules.
Read moreCheck thermostat settings
Confirm it's set to HEAT or COOL (not OFF), fan is on AUTO, and the target temperature makes sense.
Read moreTest with a manual override
Set the temp 5 degrees above or below room temp and wait 5 minutes. You should hear the system click on.
Read moreInspect thermostat wiring
Remove the cover and check for loose, corroded, or disconnected wires. Loose connections cause intermittent failures.
Read moreReplace the air filter
If the filter is dirty, replace it now. Use the correct size (printed on the old filter's frame) and the right MERV rating.
Read moreClean supply and return vents
Vacuum dust and debris from all registers. Blocked vents cause pressure imbalances and hot/cold spots.
Read moreCheck for ductwork leaks
Inspect visible ductwork in basement or attic for disconnected joints, holes, or crushed flex duct.
Read moreClear the area around the indoor unit
Remove boxes, stored items, and debris within 3 feet of the furnace or air handler for proper airflow.
Read moreInspect the blower motor
Listen for the blower fan. If the system turns on but no air comes out, the blower motor may have failed.
Read moreClean the outdoor condenser unit
Hose off dirt, leaves, and debris from the condenser fins. Blocked fins reduce cooling capacity by up to 30%.
Read moreClear 2 feet around the outdoor unit
Trim bushes, remove leaf piles, and ensure nothing blocks airflow around the condenser.
Read moreCheck the condensate drain line
A clogged drain causes water backup and can shut down the AC via the safety float switch.
Read moreInspect the evaporator coil for ice
If the indoor coil is frozen, turn the system to FAN ONLY for 2-4 hours to thaw. Ice means low airflow or low refrigerant.
Read moreCheck the pilot light or igniter
For gas furnaces: is the pilot light lit? For newer models, listen for the igniter clicking. No ignition = no heat.
Read moreInspect the gas supply valve
Verify the gas valve near the furnace is in the ON position (handle parallel to pipe). Turned-off valves are a common oversight.
Read moreCheck the furnace safety switch
The furnace door has a safety switch — if the panel isn't seated properly, the furnace won't run.
Read moreLook for furnace error codes
Most furnaces have a blinking LED on the control board. Count the blinks and check the code chart on the panel door.
Read moreDiagnose rattling or vibrating sounds
Loose screws, panels, or ductwork cause rattling. Tighten what you can access safely.
Read moreInvestigate squealing or screeching
A worn belt or failing bearing causes squealing. Turn the system off to prevent further damage and call a tech.
Read moreAddress burning or musty smells
Burning smell on first use of season is normal (dust burning off). Persistent burning or electrical smell means shut off immediately.
Read moreCheck for banging sounds in ductwork
Popping or banging when the system starts is often duct expansion. Loud banging may indicate a delayed ignition problem.
Read moreKnow when to call a professional
Refrigerant issues, gas leaks, electrical faults, and compressor failures require a licensed HVAC technician.
Read moreGet multiple repair quotes
For non-emergency repairs, get 2-3 quotes. Prices vary widely — $150 to $500+ for the same repair.
Read moreDecide: repair or replace?
If your system is 15+ years old and the repair is over 50% of replacement cost, replacing is usually smarter.
Read moreSchedule preventive maintenance
Annual tune-ups ($75-200) catch problems early and extend system life by 5-10 years.
Read moreOther repair guides