The following guide helps diagnose and resolve a Comfortmaker furnace not igniting, covering common causes, step-by-step troubleshooting, safety tips, and when to call a professional. The information is tailored for a U.S. audience and focuses on practical, reliable actions homeowners can take to restore heat safely.
| Symptom | Possible Cause | Quick Fix |
|---|---|---|
| Furnace Won’t Ignite | Thermostat, Gas Supply, Ignitor | Check thermostat, gas valve, reset furnace |
| Clicking But No Flame | Ignitor Failure, Flame Sensor | Inspect/replace ignitor or clean sensor |
| Short Cycling Or Flicker | Incorrect Flame, Pressure Switch | Clean burners, check venting |
How Comfortmaker Furnaces Ignite And Why It Matters
Comfortmaker furnaces use either a hot surface ignitor (HSI) or a direct spark ignition system to light the gas burner. The ignition system works with the control board, thermostat, gas valve, flame sensor, and safety switches to create and maintain a stable flame. Understanding these components is essential for effective troubleshooting when a Comfortmaker furnace is not igniting.
Common Causes Of A Comfortmaker Furnace Not Igniting
When a Comfortmaker furnace does not ignite, several parts and conditions are typically responsible. Common causes include a faulty ignitor, dirty flame sensor, closed gas valve, thermostat issues, tripped safety switches, or control board failures. External issues such as a power outage or blocked venting can also prevent ignition.
Ignitor Failure
A worn or cracked hot surface ignitor is among the most frequent reasons a Comfortmaker furnace will not ignite. HSIs become brittle with age and often fail without visible signs on the outside of the furnace. Ignitor resistance testing with a multimeter helps confirm failure.
Dirty Or Faulty Flame Sensor
The flame sensor detects the presence of flame and tells the control board to keep the gas valve open. Carbon buildup can cause a flame sensor to read incorrectly and shut down ignition attempts. Cleaning the sensor with fine emery cloth often restores function.
Gas Supply Or Gas Valve Problems
Insufficient gas pressure, a closed gas shutoff valve, or a faulty gas valve will prevent ignition. A homeowner can verify the gas line valve is open, but testing gas pressure or repairing valves should be left to licensed technicians due to safety and code requirements.
Thermostat Or Electrical Issues
Thermostat wiring, incorrect settings, or lack of 24VAC power to the furnace control board can stop ignition. Additionally, blown fuses, tripped breakers, or disconnected wiring can interrupt the control sequence and result in a Comfortmaker furnace not igniting.
Venting, Pressure Switch, Or Inducer Problems
Modern high-efficiency Comfortmaker furnaces rely on a powered inducer and pressure switch to verify proper venting before ignition. Blocked exhaust, failed inducer motor, or a stuck pressure switch can prevent ignition or cause repeated shutdowns during start-up.
Safety First: Precautions Before Troubleshooting
Before performing any troubleshooting, turn off power to the furnace at the breaker and switch off the gas if work involves gas components. Carbon monoxide and gas leaks pose serious hazards, so never attempt gas valve repairs without proper training and certification. If there is a smell of gas, evacuate and call the gas company or 911 immediately.
Step-By-Step Troubleshooting For Comfortmaker Furnaces Not Igniting
These steps guide homeowners through safe, logical checks to identify common causes of ignition failure. Each step is concise and designed for residential Comfortmaker furnace models with standard ignition systems.
- Verify Power And Thermostat Settings — Confirm the thermostat is set to heat and the desired temperature is above room temperature. Check the furnace switch and circuit breaker, and reset any tripped breaker.
- Listen For The Furnace Sequence — When the thermostat calls for heat, the inducer should start, then the gas valve should open and the ignitor should light. Note where the sequence stops to narrow down the cause.
- Check For Error Codes — Many Comfortmaker furnaces display LED blink codes on the control board. Count blinks and reference the model-specific error chart in the manual to identify the faulty component.
- Inspect And Clean The Flame Sensor — If the furnace lights briefly then shuts off, remove and gently clean the flame sensor with fine sandpaper or emery cloth, then reinstall.
- Test The Ignitor — Visually inspect the ignitor for cracks. Use a multimeter to measure resistance (HSI typically around 40-120 ohms depending on model). A broken ignitor or infinite resistance indicates replacement is needed.
- Verify Gas Supply And Valve Position — Ensure the gas shutoff near the furnace is open. If gas supply is suspected to be the issue, contact a licensed technician to test pressure and valve operation.
- Check Pressure Switch And Inducer — Inspect the pressure switch tubing for blockages or cracks. If the inducer fails to run, the furnace will not proceed to ignition.
- Inspect Venting For Blockage — For direct-vent furnaces check outdoors for obstructions at the intake and exhaust vents. Birds, leaves, or snow can block airflow and prevent ignition.
- Reset The Furnace — After making repairs or checks, reset the furnace by turning the power off for 30 seconds and back on. Observe the restart sequence for normal operation.
Interpreting Comfortmaker Control Board Error Codes
Comfortmaker furnaces use LED blink patterns to indicate faults. Common codes include lockout for failed ignition, flame loss, pressure switch failure, and limit switch trips. Refer to the model-specific manual for accurate code definitions and recommended actions.
When To Replace Parts Versus Calling A Technician
Homeowners can replace non-gas electrical parts like thermostats, filters, and sometimes ignitors if they are comfortable and the furnace manual allows it. However, gas valve replacement, pressure testing, control board swaps, and inducer motor repairs should be handled by licensed HVAC technicians to ensure safety and code compliance.
Maintenance Tips To Prevent Future Ignition Problems
Regular maintenance reduces the chance a Comfortmaker furnace will not ignite. Recommended tasks include annual professional tune-ups, changing the air filter every 1–3 months, cleaning the flame sensor and burners, clearing outdoor vents, and keeping the furnace area free of debris.
- Annual Inspection — A certified HVAC technician should inspect ignition components, gas connections, heat exchanger, and CO levels annually.
- Routine Filter Changes — Replace or clean filters per manufacturer guidance to maintain airflow and prevent sensor issues.
- Keep Vents Clear — Regularly check outdoor intake and exhaust terminations for blockages from vegetation or debris.
Estimated Repair Costs For A Comfortmaker Furnace Not Igniting
Repair costs vary by part and region. Typical U.S. price ranges: ignitor replacement $100–$300 including labor, flame sensor cleaning or replacement $80–$200, inducer motor replacement $300–$600, control board replacement $300–$700, gas valve replacement $300–$800. These are estimates and can vary significantly.
Finding The Right HVAC Technician And Warranty Considerations
When professional help is required, choose an HVAC contractor licensed in the service area with positive reviews and Comfortmaker experience. Check the furnace warranty for coverage of parts and labor. Document maintenance and repairs to support warranty claims.
Quick Reference Checklist For Homeowners
This checklist helps identify easy fixes before calling a technician.
- Make sure the thermostat is set to heat and batteries are fresh if applicable.
- Confirm the furnace power switch and circuit breaker are on.
- Replace or inspect the air filter.
- Look for error code blinks and note the pattern.
- Clean the flame sensor if ignition occurs briefly then stops.
- Ensure outdoor vents are clear of obstructions.
- Do not attempt gas valve repairs; call a licensed technician for gas-related issues.
FAQ: Common Questions About Comfortmaker Furnaces Not Igniting
Why Does The Furnace Click But Not Ignite?
Clicking often signals the control board attempting ignition, but a failed ignitor, blocked gas flow, or faulty gas valve can prevent flame. If clicking repeats without ignition, interruption in the ignition sequence or an electronic lockout may be present.
What If The Furnace Lights Then Shuts Off Quickly?
Brief ignition followed by shutdown usually points to a dirty flame sensor or poor flame detection. Cleaning or replacing the flame sensor typically resolves the issue.
Can A Dirty Filter Cause A Furnace Not To Ignite?
A very clogged filter can restrict airflow and trip pressure or limit switches, preventing ignition. Replacing the filter is a simple step that can sometimes restore normal operation.
Resources And Manuals
Owners should keep the Comfortmaker furnace model number and serial number available to access the correct manual and wiring diagrams. Manufacturer documents and replacement part numbers are essential for accurate troubleshooting and ordering parts.
Note: This article provides general guidance and estimation. For any issues involving gas, combustion, or suspected carbon monoxide risk, contact a licensed HVAC technician immediately. If there is a strong odor of gas, leave the premises and call emergency services.