Reliable Winter Heat Starts with Fall Furnace Maintenance

A clogged furnace filter restricts airflow and forces your blower motor to work harder, reducing efficiency and potentially causing the furnace to overheat or cycle incorrectly. We replace your filter with a new one of the proper MERV rating for your system. We also inspect the burner assembly (where gas mixes with air and ignites) and the combustion chamber walls for deposits and buildup. If visible deposits are present, we carefully clean the burner nozzles and combustion chamber using appropriate tools and solvents. This cleaning restores efficient fuel mixing and combustion.

• Replace furnace filter with new filter matching system specifications
• Inspect burner assembly for carbon deposits, rust, or damage
• Clean burner nozzles and pilot area if clogged or dirty
• Wipe combustion chamber walls to remove soot and carbon buildup
• Inspect gas valve adjustment and verify it’s set correctly
• Check blower wheel for dust accumulation and clean if needed

The technician inserts a flue gas analyzer probe into your furnace vent pipe and records combustion readings: oxygen level, CO₂ level, and carbon monoxide concentration. These readings reveal whether fuel and air are mixing correctly, whether combustion is complete, and critically, whether any CO is being produced. They compare readings against manufacturer specifications for your furnace model. If CO is detected in the exhaust (above safe limits), we stop operation and diagnose the cause—usually a burner issue or venting problem. They also perform a non-invasive CO test in your home air to verify your family isn’t being exposed to carbon monoxide. This test alone is worth the maintenance cost for peace of mind.

• Connect flue gas analyzer to vent pipe and record O₂, CO₂, and CO readings
• Compare combustion readings against furnace manufacturer specifications
• Verify carbon monoxide levels are below safe limits (ideally zero)
• Perform home air CO test to confirm no CO leak into living spaces
• Document all readings for your safety records
• If abnormalities found, diagnose cause and recommend repairs

The heat exchanger is the component where combustion heat is transferred to your home’s air. If it develops cracks, hot combustion byproducts (including carbon monoxide) can leak into your home. Our technician visually inspects the heat exchanger exterior for visible cracks, separation of seams, corrosion, or discoloration. They also check the vent pipe for cracks, rust, or gaps that could allow exhaust to leak into your home or allow outside air to enter. Any cracks or venting problems are flagged immediately—a cracked heat exchanger requires furnace shutdown until replacement.

• Visually inspect accessible heat exchanger surfaces for cracks or corrosion
• Check vent pipe for rust, holes, or loose joints that allow gas leaks
• Verify vent termination is proper (typically 3+ feet above roof or adjacent to wall)
• Inspect chimney or flue for blockages, cracks, or deterioration
• Check draft safety switch responsiveness (sensor that verifies exhaust venting)
• Document findings and photograph any concerns for your records

The furnace relies on several electrical safety controls. Our technician uses a multimeter to verify proper voltage at the thermostat (24V AC), igniter or pilot valve, and blower motor. They test the igniter for proper spark output (if equipped with electronic ignition), verify thermostat wiring continuity, and test limit switches and draft safety switches for responsiveness. A limit switch prevents overheating by shutting off the burner if internal temperature gets too high. A draft switch ensures the vent is clear before burner ignition. Both are critical safety components. Electrical testing takes 15–20 minutes but reveals failures before they cause emergency shutdowns.

• Test thermostat voltage (should read 24V AC, stable)
• Test igniter spark output or pilot valve electrical signal
• Verify igniter continuity and spark gap (if removable electrode type)
• Test limit switch responsiveness using manual button test
• Test draft safety switch to confirm proper activation at venting
• Inspect all electrical connections for corrosion and tighten if loose
• Check for tripped breakers or blown fuses in furnace control panel

Your furnace’s blower motor moves heated air through your home’s ducts. We listen to the motor during operation for unusual grinding, squealing, or rattling sounds that indicate bearing wear. We measure electrical current draw on the blower to ensure it’s within normal range—excessive current indicates motor strain or impending failure. We also verify the blower wheel spins freely and isn’t blocked by debris or damaged fan blades. If your furnace has a variable-speed blower (common in high-efficiency units), we test its operation through different speeds to confirm proper control response.

• Listen to blower motor during operation for unusual noises
• Feel blower discharge temperature and verify heated air is warm
• Measure electrical current draw on blower startup and running operation
• Visually inspect blower wheel for damage, debris, or blockages
• Spin blower wheel by hand (when power is off) to verify free rotation
• Test thermostat control signal to blower (G wire continuity)

Once all components have been inspected and tested, the technician allows the furnace to run through a complete heating cycle. They measure the temperature rise across the furnace—placing thermometers at the return-air duct (air entering the furnace) and supply duct (heated air leaving the furnace). The temperature difference tells us whether the furnace is producing the amount of heat it should. They also listen for smooth operation: normal whoosh of air, one or two startup clicks, and a single shutdown cycle. Unusual sounds, erratic cycling, or weak temperature rise indicates remaining problems that need attention.

• Measure return-air and supply-air temperatures to calculate heat output
• Compare temperature rise against furnace specifications for your model
• Verify furnace cycles properly (ignition, heating, shutdown sequence)
• Confirm blower continues running for proper duration after burner shuts off
• Listen for normal operation sounds and note any unusual noise
• Verify thermostat responsiveness to setpoint changes during test run

You’ll receive written documentation of every inspection and test: filter replaced, combustion analysis results, electrical tests, component conditions, and any issues identified. We explain seasonal operation: what sounds are normal (clicks at startup, whoosh of air, hum of blower), what problems to watch for (difficulty igniting, weak heat, strange noises), and what maintenance timing works best for your system. If developing issues were identified (corrosion on connections, slight gas pressure variation, blower noise), we recommend monitoring or next-season follow-up. For maintenance plan members, we schedule your next appointment before we leave.

• Provide written maintenance report with all test results and findings
• Review combustion analysis and CO testing results for your peace of mind
• Explain any issues found and recommend repair timing (urgent vs. next season)
• Discuss seasonal operation and what sounds/behaviors are normal
• Leave emergency contact information for winter heating questions
• Schedule next maintenance visit for plan members (typically 12 months)
• Answer questions about furnace operation and winter heating readiness