A thorough furnace tune-up is significantly more involved than changing a filter and confirming the system turns on. Here's what a proper heating maintenance visit should include and why each step matters.
Annual furnace maintenance is one of those services where the quality varies enormously between contractors. A brief operational check and a filter swap — completed in 20 minutes — is not the same thing as a thorough inspection and tune-up that catches developing problems before they become heating emergencies. Understanding what a proper furnace maintenance visit should include helps you evaluate whether you're receiving real value for the service you're paying for.
Why Furnace Maintenance Is Different From AC Maintenance
Furnace maintenance involves safety inspections that air conditioning maintenance does not. A gas furnace combusts fuel inside the home, produces carbon monoxide as a byproduct, and relies on safety controls and mechanical integrity to prevent those combustion gases from entering the living space. Confirming those safety systems are functioning correctly — and inspecting the heat exchanger for signs of failure — is not optional in a quality maintenance visit.
Filter Inspection and Replacement
The maintenance visit begins with the air filter. The technician checks the filter condition and replaces it if needed — or confirms the homeowner has been doing so. A clean filter is essential for adequate airflow; a clogged filter is one of the leading causes of furnace problems and overheating. If a high-MERV filter has been installed, the technician should confirm it is compatible with the system's blower specifications.
Heat Exchanger Inspection
This is the most safety-critical component of furnace maintenance. The technician inspects the heat exchanger for cracks, holes, rust, or signs of separation — any of which can allow combustion gases including carbon monoxide to enter the heated airstream. Inspection methods include visual examination with a flashlight and mirror, camera scope where accessible, and in some cases flame or chemical tests to detect breaches. A cracked heat exchanger is grounds for taking the furnace out of service.
Burner Cleaning and Inspection
Gas burners accumulate dust, debris, and oxidation over a heating season. Dirty burners produce uneven combustion, can cause delayed ignition (which produces the banging sound discussed in another article), and may burn less efficiently than clean burners. The technician removes and cleans the burners, confirms the flame appearance is correct (steady, blue, even across all burners), and checks the burner orifices for blockage or damage.
Igniter and Flame Sensor Service
The hot surface igniter heats up to ignite the gas on each heating cycle. Over time, igniters become brittle with use. A technician measures the igniter's electrical resistance and compares it to the manufacturer's specification — a reading outside the acceptable range predicts imminent failure and is a reasonable candidate for proactive replacement. The flame sensor is cleaned to remove oxidation that can prevent it from reliably detecting the burner flame.
Electrical Component Testing
Capacitors (which assist motor startup), contactors, relays, and control board terminals are inspected and tested. Capacitor readings are measured and compared to rated specifications — a capacitor trending toward the lower end of its acceptable range is a candidate for proactive replacement before it fails mid-season. Wiring connections are checked for tightness and signs of arcing or heat damage.
Blower Motor Inspection and Lubrication
The blower motor circulates air through the heat exchanger and duct system. The motor's amperage draw is measured under operating conditions — a reading above the motor's rating indicates the motor is working harder than designed, often due to a dirty blower wheel or restricted airflow. Motors with oil ports are lubricated. The blower wheel is inspected for dust accumulation that reduces airflow and creates imbalance.
Flue and Venting Inspection
The furnace flue carries combustion exhaust out of the home. The technician inspects the flue pipe connections for separation, rust, or blockage, confirms the flue is properly pitched for drainage (on condensing furnaces), and checks that the flue termination at the exterior is clear and unobstructed. A blocked or separated flue can cause combustion gases to back-draft into the home.
Safety Control Testing
The high-limit switch (which shuts off the burners when the heat exchanger overheats) and pressure switches (which confirm proper draft before allowing ignition) are tested for correct operation. These controls exist as backup protection against unsafe conditions, and confirming they function correctly is part of a responsible maintenance visit.
System Startup and Temperature Testing
After completing the inspection and service items, the technician starts the system and monitors its operation through a complete heating cycle. Temperature rise across the heat exchanger (the difference between the supply and return air temperatures) is measured and compared to the furnace's specification range — too low or too high indicates a problem with airflow or combustion. The technician confirms the system cycles normally and documents findings.
Cervino Heating & Air performs thorough furnace tune-ups for homeowners throughout Nashville, Antioch, and Middle Tennessee. Contact us to schedule your fall heating maintenance before cold weather arrives.
Need Professional HVAC Service?
Cervino Heating & Air serves Nashville, Antioch, and all of Middle Tennessee with honest pricing and same-day service.