Your HVAC system isn't working right, and you need answers. Before calling for an expensive service call, there are several things you can check yourself that might solve the problem — or at least help you explain the issue to a technician.
Here's a practical troubleshooting guide.
Check These First (Free Fixes)
Start with the basics:
Thermostat — Is it set correctly? Check mode (heat/cool), temperature setting, and batteries
Air filter — A clogged filter is the #1 cause of HVAC problems. Check it now
Circuit breakers — Check both indoor and outdoor unit breakers. Reset if tripped
Vents — Are supply and return vents open and unobstructed?
Outdoor unit — Is it running? Is it blocked by debris, snow, or plants?
These basic checks solve roughly 30% of HVAC service calls.
Common Causes You Can Identify
If the system runs but doesn't heat/cool well: - Dirty filter restricting airflow - Blocked or closed vents - Thermostat set incorrectly - Outdoor unit blocked by debris
If the system won't turn on: - Tripped circuit breaker - Thermostat batteries dead - Safety switch triggered (some furnaces have a door switch) - Power outage to outdoor unit
If it makes unusual noises: - Banging: Could be ignition delay or loose part - Squealing: Belt or bearing issue - Rattling: Loose panel or debris in unit - Clicking: Normal at startup, concerning if continuous
When to Call a Professional
Call immediately if: - You smell gas (call the gas company too) - CO detector is alarming - You see smoke or smell burning - Breaker keeps tripping after reset - Water is leaking and causing damage
Schedule service if: - Basic troubleshooting didn't resolve the issue - System short-cycles (turns on and off frequently) - Strange odours persist - Uneven heating/cooling throughout the home - Energy bills have spiked unexpectedly
What to tell the technician: - When the problem started - What you've already checked - Any unusual sounds, smells, or behaviours - When the system was last serviced
Typical Repair Costs
Minor repairs: - Thermostat replacement: $150 - $300 - Capacitor/contactor: $150 - $300 - Ignitor or flame sensor: $200 - $400 - Fan motor: $300 - $600
Major repairs: - Compressor: $1,500 - $2,500 - Heat exchanger: $1,500 - $3,000 - Evaporator/condenser coil: $1,000 - $2,500
Rule of thumb: If repair cost exceeds 50% of replacement cost, and the equipment is over 12 years old, replacement usually makes more sense.
The Bottom Line
Start with the basics — filter, thermostat, breakers — before calling for service. Many HVAC problems have simple solutions. But if you've checked everything and the problem persists, don't wait — small issues become expensive problems.
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