Furnace Ignition Failure: 6 Causes Michigan Techs Fix

NEXT Heating & Cooling • March 2, 2026 • 9 min read

Your thermostat calls for heat. The furnace blower kicks on. You hear the click of the gas valve. Then nothing. Three attempts, three failures, and your furnace goes into safety lockout mode while the temperature drops outside your Sterling Heights home.

Furnace ignition failure is one of the most common service calls we handle during Michigan winters. When outdoor temperatures hit single digits or below zero during a polar vortex, a furnace that won't light becomes an emergency. The good news: most ignition failures stem from six specific causes, and experienced HVAC technicians can diagnose them quickly.

Our heating and cooling services in Metro Detroit include comprehensive furnace diagnostics using the same systematic approach for every ignition failure. We'll walk you through what actually happens during the ignition sequence, why it fails, and what homeowners in Macomb, Oakland, and St. Clair counties should know about this critical system.

How Modern Furnace Ignition Systems Work

Most furnaces installed in Michigan homes over the past 20 years use electronic ignition instead of a standing pilot light. The two main types are hot surface igniters (HSI) and intermittent pilot systems. Hot surface igniters dominate newer installations from manufacturers like Carrier, Lennox, Trane, and Rheem.

Here's the normal ignition sequence when your thermostat calls for heat:

1. The control board receives the signal and starts the induced draft blower to clear any residual gas from the heat exchanger.
2. A pressure switch confirms adequate airflow through the venting system.
3. The control board energizes the hot surface igniter, which heats to approximately 2,500°F and glows bright orange.
4. After 15-30 seconds of preheat, the gas valve opens and gas flows to the burners.
5. The gas ignites immediately when it contacts the glowing igniter.
6. The flame sensor (a thin metal rod positioned in the flame path) confirms ignition by detecting flame current.
7. If the sensor confirms flame presence, the gas valve stays open and the furnace continues heating.

This entire sequence takes 30-45 seconds under normal conditions. If any step fails, the furnace shuts down and tries again. After three failed attempts, most systems enter a safety lockout that requires manual reset or a waiting period of 1-3 hours.

6 Most Common Causes of Furnace Ignition Failure

Our technicians see the same ignition problems repeatedly across Southeast Michigan. These six issues account for roughly 85% of the ignition failure calls we handle in Troy, Warren, and Clinton Township.

1. Dirty or Cracked Flame Sensor

The flame sensor is a thin metal rod that sits directly in the flame path after ignition. It works by detecting the electrical conductivity of the flame itself. When the flame heats the sensor rod, a small electrical current (measured in microamps) flows back to the control board as proof that combustion is happening.

Over time, carbon buildup coats the sensor rod. This insulating layer blocks the electrical signal even when flame is present. The control board interprets this as "no flame detected" and shuts the gas valve within 3-5 seconds. You'll hear ignition happen, see the flame light, then watch it shut off almost immediately.

Flame sensor cleaning takes about 10 minutes with fine-grit sandpaper or emery cloth. We gently polish the rod to bare metal without bending or damaging it. A cracked or corroded sensor requires replacement, which costs $150-$250 including labor in most Metro Detroit service calls.

This is the single most common cause of ignition failure we see, especially in furnaces that haven't had seasonal furnace and AC tune-ups in the past 2-3 years.

2. Failed Hot Surface Igniter

Hot surface igniters are fragile ceramic components that crack or break from thermal stress. They typically last 3-7 years depending on furnace runtime and cycling frequency. When an igniter fails, you'll hear the draft blower run and the gas valve click, but no ignition occurs because there's no heat source to light the gas.

Visual inspection usually reveals the problem. A cracked igniter shows visible breaks in the ceramic element. A weak igniter glows dim orange or yellow instead of bright white-orange. Some igniters fail electrically without visible damage, requiring voltage testing to confirm.

Igniter replacement is straightforward but requires care. The ceramic element breaks easily if bumped or touched with oils from bare skin. Professional replacement costs $200-$350 depending on the furnace model and igniter type. Carrier, Lennox, and Trane furnaces each use specific igniter designs that aren't always interchangeable.

We always carry common igniter types on our service trucks for same-day furnace repair when temperatures drop and homeowners can't wait for parts orders.

3. Gas Valve Malfunction

The gas valve controls fuel flow to the burners. It's a solenoid-operated device that opens when the control board sends voltage after confirming the igniter is hot and all safety switches are closed. Gas valve problems fall into two categories: valves that won't open and valves that won't close.

A valve that won't open prevents ignition entirely. You'll hear the igniter glow and see it turn bright orange, but no gas flows to the burners. This can result from a failed solenoid coil, mechanical blockage inside the valve body, or low gas pressure from the utility supply.

A valve that won't close fully creates a different problem. Small amounts of gas leak into the heat exchanger between heating cycles, creating a dangerous condition. Modern furnaces detect this through flame rollout switches and pressure switch monitoring, shutting down the system before hazardous gas buildup occurs.

Gas valve replacement costs $350-$600 including labor. We never attempt to repair gas valves internally. The safety risk isn't worth the minimal cost savings. Michigan mechanical code requires licensed contractors to handle all gas valve work, which is why DIY repairs on this component are both illegal and dangerous.

4. Pressure Switch Failure

The pressure switch (sometimes called a draft pressure switch) confirms that the induced draft blower is creating adequate negative pressure to safely vent combustion gases. It's a safety device that prevents furnace operation if venting is blocked or the blower isn't running.

When the draft blower runs, it creates a vacuum that pulls a rubber diaphragm inside the pressure switch. This closes electrical contacts, sending a signal to the control board that it's safe to proceed with ignition. If the switch doesn't close, the ignition sequence stops before the igniter even heats up.

Pressure switch problems stem from several causes. The rubber sensing tube can crack or disconnect, preventing pressure detection. The switch itself can fail mechanically. More commonly, the condensate drain line backs up, creating a water trap that blocks pressure sensing. This is especially common in Michigan basements where humidity and temperature swings cause excessive condensation.

Diagnosis requires a manometer to measure actual draft pressure and compare it to the switch setpoint (usually stamped on the switch body in inches of water column). Pressure switch replacement costs $150-$300, but clearing a blocked condensate line might solve the problem for just the service call fee.

5. Blocked Burners or Orifices

Gas burners and orifices can accumulate dust, rust, or debris that restricts gas flow. This creates weak, yellow flames instead of the strong blue flames needed for proper combustion. The flame sensor detects the weak flame as insufficient and shuts down the gas valve.

We see this most often in furnaces located in dusty basements or utility rooms without proper filtration. The burner ports (small holes where gas exits) can clog partially, causing uneven flame patterns. In severe cases, rust flakes from aging heat exchangers fall into the burner assembly and block multiple ports.

Burner cleaning involves removing the burner assembly, brushing out the ports with a wire brush, and vacuuming all debris. For furnaces over 15 years old, we inspect carefully for heat exchanger corrosion during this process. Cracked heat exchangers require furnace replacement for safety reasons.

If you're experiencing repeated ignition problems in an aging furnace, it might be time to consider your options. Our guide to the best furnace brands for Michigan homes helps homeowners understand modern efficiency and reliability improvements.

6. Control Board Issues

The control board (also called the integrated furnace controller or IFC) orchestrates the entire ignition sequence. It's the computer that monitors all sensors, controls timing, and shuts down the system when safety conditions aren't met. Control board failures can cause intermittent ignition problems that are difficult to diagnose without proper testing equipment.

Common control board problems include failed relay contacts that won't energize the igniter, corrupted software that disrupts timing sequences, and damaged circuitry from power surges. Michigan ice storms and summer thunderstorms frequently cause power fluctuations that damage sensitive electronics.

We test control boards by measuring voltage output at each stage of the ignition sequence. A board that sends 24 volts to the igniter but fails to open the gas valve after the proper delay has a failed relay. A board that won't energize the draft blower has a different failure mode requiring different diagnosis steps.

Control board replacement is expensive, typically $400-$800 depending on the furnace brand and model. We always verify that the board is actually failed before recommending replacement, because misdiagnosis wastes money and doesn't solve the real problem. Sometimes what appears to be a board failure is actually a wiring issue or a failed sensor sending incorrect signals to an otherwise functional board.

Michigan-Specific Ignition Challenges

Southeast Michigan creates unique conditions that stress furnace ignition systems beyond what manufacturers test for in controlled lab environments. Understanding these regional factors helps explain why certain failures happen more frequently here than in milder climates.

Polar Vortex and Gas Pressure Variations

When outdoor temperatures drop below zero during polar vortex events, natural gas demand spikes across the entire region. Utility companies maintain adequate pressure for safety, but the pressure at your home's gas meter can drop from the normal 7 inches of water column to 5-6 inches during peak demand hours.

This reduced pressure affects ignition reliability. Gas valves calibrated for normal pressure may not deliver enough fuel for immediate ignition when pressure drops. The igniter glows, the valve opens, but ignition is delayed by 2-3 seconds. This delay can trigger the flame sensor timeout, causing shutdown even though ignition would have occurred with slightly more time.

We see this most often in homes with long gas line runs from the meter to the furnace, or in neighborhoods at the end of distribution branches. The solution sometimes requires gas line upsizing or pressure regulator adjustment, work that requires coordination with the utility company.

Basement Condensation and Corrosion

Michigan basements cycle through extreme humidity swings. Summer humidity condenses on cold furnace components. Winter condensation forms when warm indoor air contacts cold metal surfaces. This constant moisture exposure corrodes flame sensors, rusts burner assemblies, and degrades electrical connections.

High-efficiency furnaces (90%+ AFUE) produce significant condensate as part of normal operation. A single-family home furnace can generate 5-10 gallons of acidic condensate per day during peak heating season. If the condensate drain system backs up or freezes, this water floods the pressure switch sensing tubes and triggers safety shutdowns.

We recommend condensate pump installation for furnaces in basements prone to flooding or homes where the floor drain is higher than the furnace condensate outlet. This $200-$300 upgrade prevents 90% of condensate-related ignition failures we see in Shelby Township and Chesterfield homes.

Power Surge Damage from Ice Storms

Ice storms knock out power across Southeast Michigan several times each winter. When power returns, the voltage surge can damage control boards, igniters, and gas valve solenoids. We see a spike in ignition failure calls in the 24-48 hours following major outages.

Whole-house surge protection costs $300-$500 installed and protects all 240-volt appliances including your furnace, air conditioner, and water heater. For critical HVAC equipment, we also recommend dedicated surge protectors on the furnace electrical circuit, especially for homes in rural areas prone to frequent outages.

If your furnace experiences ignition problems after a power outage, the issue might be related to other electrical components. Our article on why furnaces won't turn on covers the full diagnostic process including electrical issues.

When to Call for Professional Furnace Repair

Furnace ignition systems involve natural gas, high-voltage electricity, and safety controls designed to prevent explosions and carbon monoxide poisoning. This isn't a system where trial-and-error troubleshooting is safe or advisable.

Call a licensed HVAC contractor immediately if you experience any of these conditions:

• You smell natural gas (a rotten egg odor added to otherwise odorless gas) near the furnace or anywhere in your home. Leave immediately and call your gas utility emergency line from outside.
• The furnace attempts ignition three times and then locks out repeatedly, even after you reset the system.
• You see yellow or orange flames instead of blue flames during normal operation.
• The furnace makes loud booming sounds during ignition, indicating delayed ignition and gas buildup.
• Your carbon monoxide detector alarms, or family members experience headaches, dizziness, or nausea that improve when leaving the house.

Professional diagnosis of ignition failure follows a systematic process. Our NATE-certified HVAC technicians use the following approach on every service call:

1. Visual inspection of the entire ignition system including the igniter, flame sensor, gas valve, and burner assembly.
2. Control board diagnostic code reading using LED flash patterns or digital displays.
3. Voltage testing at each component to verify proper electrical supply and control signals.
4. Gas pressure measurement at the furnace inlet and at the manifold to confirm adequate supply.
5. Draft pressure testing to verify proper venting and pressure switch operation.
6. Flame sensor current measurement to confirm adequate flame detection signal.
7. Combustion analysis using a flue gas analyzer to verify safe, efficient operation after repairs.

This diagnostic process takes 30-60 minutes depending on the complexity of the problem. We explain findings in plain language and provide repair options with upfront pricing before starting any work.

Cost Reality for Common Ignition Repairs in Southeast Michigan:

Flame sensor cleaning: $89-$150 (often included in tune-up service)

Hot surface igniter replacement: $200-$350

Pressure switch replacement: $150-$300

Gas valve replacement: $350-$600

Control board replacement: $400-$800

Complete burner assembly cleaning: $150-$250

These prices include parts, labor, and warranty on the work performed. Emergency service calls during nights, weekends, or holidays typically add $75-$150 to the base service fee. Our reliable HVAC contractor pricing is transparent with no hidden fees or upselling pressure.

Preventing Ignition Failure with Maintenance

Most ignition failures develop gradually over months or years. Regular maintenance catches problems before they cause complete system failure, especially during the coldest weeks of winter when you need heat most.

A professional furnace tune-up includes specific ignition system maintenance that homeowners can't safely perform themselves:

• Flame sensor cleaning and current measurement to verify proper operation
• Visual inspection of the hot surface igniter for cracks or damage
• Burner assembly removal, cleaning, and inspection for proper flame pattern
• Gas pressure measurement and adjustment if needed
• Pressure switch testing and condensate drain clearing
• Control board inspection for signs of overheating or component failure
• Electrical connection tightening at all ignition components
• Combustion analysis to verify safe, efficient operation

The Next Care Plan provides this comprehensive maintenance twice per year (fall furnace tune-up and spring AC tune-up) for just $5 per month. Members also receive priority scheduling, 10% discounts on repairs, and no service call fees.

Over 35 years serving Southeast Michigan, we've found that homeowners with regular maintenance experience 70-80% fewer emergency breakdowns than those who skip annual service. The cost of a single emergency igniter replacement during a January cold snap pays for three years of preventive maintenance.

For homeowners who've experienced repeated ignition problems despite repairs, it might indicate an aging furnace nearing the end of its service life. Similar to how certain Goodman furnace repairs become uneconomical after 15-20 years, ignition system failures in older units sometimes signal it's time to consider replacement rather than continued repairs.

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Frequently Asked Questions About Furnace Ignition Failure

How do I know if my furnace igniter is bad? +

A failed igniter typically shows visible cracks in the ceramic element, glows dim orange or yellow instead of bright white-orange, or doesn't glow at all when the furnace calls for heat. You'll hear the draft blower run and the gas valve click, but no ignition occurs. Some igniters fail electrically without visible damage, requiring voltage testing by a technician to confirm. If your furnace attempts ignition three times and then locks out without lighting, a bad igniter is one of the most common causes.

Can I clean my furnace flame sensor myself? +

Homeowners with basic mechanical skills can clean a flame sensor, but it requires turning off gas and electrical power to the furnace first. The sensor is a thin metal rod near the burners, held by a single screw. Remove it carefully, polish the rod with fine-grit sandpaper or emery cloth until it's shiny bare metal, and reinstall without bending. However, if you're not comfortable working around gas appliances or if cleaning doesn't solve the ignition problem, call a licensed HVAC technician. Improper reinstallation can create safety hazards.

Why does my furnace ignite then shut off after a few seconds? +

This classic symptom indicates a dirty or failed flame sensor. The furnace ignites successfully, but the flame sensor doesn't detect the flame current due to carbon buildup or corrosion on the sensor rod. The control board interprets this as "no flame present" and shuts the gas valve within 3-5 seconds for safety. Cleaning or replacing the flame sensor solves this problem in about 90% of cases. Less commonly, a weak gas valve, incorrect gas pressure, or control board issues can cause the same symptom.

How much does it cost to fix furnace ignition problems in Michigan? +

Repair costs vary by component and labor complexity. Flame sensor cleaning costs $89-$150 and is often included in tune-up service. Hot surface igniter replacement runs $200-$350. Pressure switch replacement costs $150-$300. Gas valve replacement is more expensive at $350-$600. Control board replacement is the most costly at $400-$800. These prices include parts, labor, and warranty on work performed. Emergency service during nights, weekends, or holidays typically adds $75-$150 to the base service fee. Proper diagnosis before repair prevents unnecessary part replacement and wasted money.

How long do furnace igniters typically last? +

Hot surface igniters typically last 3-7 years depending on furnace runtime and cycling frequency. Furnaces that short-cycle (turn on and off frequently) wear out igniters faster because each heating cycle stresses the ceramic element through thermal expansion and contraction. High-efficiency furnaces with longer burn times between cycles tend to get more years from an igniter. Michigan's long heating season and extreme cold snaps put more stress on igniters than milder climates. Once an igniter reaches 5-6 years old, it's wise to have a spare on hand or budget for replacement within the next year or two.

What causes furnace ignition failure in cold weather? +

Cold weather creates several ignition challenges specific to Michigan. Natural gas pressure can drop during polar vortex events when regional demand spikes, reducing fuel delivery to the burners. Condensation from temperature swings corrodes flame sensors and electrical connections. Frozen condensate drain lines back up and trigger pressure switch safety shutdowns. Power outages from ice storms damage control boards and igniters when electricity returns with voltage surges. Additionally, furnaces run more frequently in extreme cold, accelerating wear on igniters and other components. Regular fall maintenance before winter hits prevents most cold-weather ignition failures.