Atwood Furnace Ignition Lockout Fault: Causes, Troubleshooting, and Fixes

The Atwood furnace ignition lockout fault is a common error in RV and marine heating systems that prevents the furnace from lighting after repeated failed attempts. This article explains what the fault means, the most likely causes, step-by-step diagnostics, safe repair options, and prevention tips to restore reliable heat. The guidance is applicable to Atwood and Suburban models that share similar ignition control logic.

Fault Indicator	Typical Meaning	Quick First Step
Ignition Lockout	No ignition after multiple tries; safety lock prevents further attempts	Reset power or cycle thermostat; check for error flash codes
Ignition Attempt But No Flame	Pilot or main burner not lighting; possible gas, spark, or sensor issue	Verify propane supply and tank valve position
Flame Detected Then Lost	Intermittent flame sense or airflow problem	Inspect flame sensor and venting for blockage

What The Atwood Furnace Ignition Lockout Fault Means

The ignition lockout fault is a protective state where the furnace controller stops attempting to light the burner after a set number of failed ignition cycles. This prevents unburned gas buildup and potential safety hazards. Lockout usually requires human intervention such as resetting power, fixing the underlying issue, and then allowing the controller to attempt ignition again.

How The Ignition Sequence Works

Understanding the normal ignition sequence helps diagnose lockout. The controller first calls for heat and opens the combustion air blower and gas valve. An ignition spark or hot surface igniter attempts to light the pilot or main burner. The flame sensor must detect a stable flame within a short period. If flame is not detected, the controller shuts the gas off and retries; after several failures, it enters lockout.

Common Causes Of Ignition Lockout

• Propane Supply Issues: Empty tank, closed tank valve, or regulator failure can prevent gas flow.
• Faulty Igniter/Spark: Worn or broken igniter electrodes or problematic ignition modules cause no spark.
• Dirty Or Misaligned Flame Sensor: Carbon buildup or corrosion prevents flame detection.
• Blocked Venting Or Combustion Air: Debris, nests, or restricted ducts impede airflow and flame stability.
• Gas Valve Or Solenoid Failure: Mechanical or electrical failure prevents gas delivery.
• Wiring Or Connector Issues: Loose, corroded, or damaged wires interrupt signals between thermostat, control board, and components.
• Thermostat Or Control Board Faults: Incorrect signals or defective controls can trigger lockout.
• Low Battery/Power Problems: RV battery voltage below required levels may disrupt ignition and sensing circuits.

Diagnostics: What To Check First

Begin with the most likely and easiest-to-test causes. Safety first: Always work in a well-ventilated area and avoid open flames during checks. Turn off the furnace and propane supply before inspecting internal components.

1. Verify Propane Supply

Confirm the propane tank has gas and the main tank valve and any camper-style shutoff valves are open. Check for frozen regulators in cold climates and listen for hissing at the furnace when the controller tries to open the valve.

2. Check For Error Codes And Lights

Many Atwood units flash an LED or provide a diagnostic code. Refer to the furnace manual for the meaning of flash sequences. Record the code before attempting resets.

3. Cycle Power To Reset Lockout

Resetting power can clear the lockout state and allow a fresh start after repairs. Switch off furnace power at the breaker or disconnect 12V power for 30 seconds, then restore power and observe the ignition sequence.

4. Inspect Igniter And Electrode Gap

Visually inspect the spark electrode for cracks, heavy carbon, or large gaps between electrode and burner. Clean gently with a soft brush and set the gap per manufacturer specs. Replace a damaged igniter.

5. Test Flame Sensor Function

The flame sensor (thermocouple or flame rod) must detect ionization current. Clean buildup with fine emery cloth and ensure the sensor is correctly positioned in the flame path. Replace if corroded or if cleaning doesn’t restore detection.

6. Examine Venting And Combustion Air

Confirm exhaust and intake vents are clear of debris, insects, and snow. Blocked vents can cause incomplete combustion and failed flame detection. Inspect internal ducting for obstructions.

7. Check Wiring, Connectors, And Grounding

Look for burnt, corroded, or loose connectors at the control board, igniter, flame sensor, and gas valve. Ensure the furnace chassis has a solid ground connection to the RV frame or battery negative.

8. Verify Gas Valve Operation

With safety precautions, observe whether the gas valve opens when the controller calls for ignition. A multimeter can test for the proper control voltage, but avoid forcing disassembly unless qualified.

Step-By-Step Troubleshooting Guide

This sequence moves from simple to more advanced tasks to isolate the cause of an Atwood furnace ignition lockout fault.

1. Confirm propane tank is not empty and valves are open. Replace or refill tank if needed.
2. Reset furnace power for 30 seconds to clear lockout, then monitor the initial ignition attempts for flash codes or unusual behavior.
3. Listen for the gas valve click and look for a spark; if no spark, inspect and replace igniter. If there is a spark but no flame, suspect gas delivery.
4. Clean the flame sensor and ensure correct placement; test again.
5. If flame lights but then goes out, inspect venting, blower operation, and flame stability.
6. Measure control voltages with a multimeter if comfortable: check 12V supply to the control board, ignition coil output, and solenoid activation voltage to the gas valve.
7. If all checks pass and the problem persists, replace the control board or gas valve only after confirming other components were tested, or consult a qualified technician.

Safety Precautions And Best Practices

Working on fuel-burning appliances involves risks. Always shut off propane and electrical power before internal inspections. Ensure the work area is ventilated to avoid gas accumulation. Use a propane leak detector spray or soapy water to test joints for leaks after repairs. If a person smells significant gas or detects a leak, evacuate and contact emergency services.

Preventive Maintenance To Avoid Lockouts

Regular maintenance reduces the chance of ignition lockout. Recommended tasks include annual furnace inspections, cleaning the flame sensor and burner assembly, checking vents for blockages, exercising valves and switches, and keeping battery voltage at healthy levels. Replace worn igniters proactively and keep the RV propane system serviced per campground or OEM guidance.

When To Call A Professional

Call a certified RV technician or licensed gas appliance repair professional if troubleshooting indicates a failing gas valve, control board, or internal wiring issues beyond simple cleaning and inspection. Professional service is also advised when leak repair, regulator replacement, or complex electrical diagnostics are required.

Common Replacement Parts And Tools

Having the right parts and tools speeds repairs. Typical parts for ignition lockout include replacement igniter electrodes, flame sensors, gas valves, and control boards compatible with Atwood or equivalent models.

Item	Purpose
Igniter Electrode	Creates spark for ignition; wears over time
Flame Sensor/Thermocouple	Detects flame; sensitive to carbon and corrosion
Gas Valve/Solenoid	Controls fuel flow; failure stops gas delivery
Control Board	Manages ignition sequence and lockout logic

Essential tools include a multimeter, insulated screwdrivers, socket set, fine emery cloth, leak detector solution, and a service manual or wiring diagram for the specific furnace model.

Troubleshooting Checklist For Field Use

• Confirm propane supply and tank valve open.
• Check for diagnostic flash codes and log them.
• Reset power to clear lockout and attempt ignition.
• Inspect igniter and electrode gap for visible spark.
• Clean flame sensor and verify flame position.
• Clear intake and exhaust vents of obstructions.
• Inspect wiring, grounds, and connectors for corrosion.
• Observe gas valve operation and listen for clicks.
• Check battery voltage and charging system health.
• Replace suspect components one at a time and retest.

Frequently Asked Questions

What Does The Ignition Lockout Light Mean On An Atwood Furnace?

The ignition lockout light indicates the control board has detected multiple failed ignition attempts and has temporarily disabled further attempts to protect against gas buildup. Reset and diagnose the cause before allowing the furnace to run.

Can A Weak Battery Cause Ignition Lockout?

Yes. Low 12V battery voltage can prevent the control board from powering the igniter, blower, or sensors correctly, leading to ignition failures and lockout. Ensure a healthy battery or connect to shore power during troubleshooting.

How Many Ignition Attempts Before Lockout?

Most Atwood-style controllers attempt ignition three to five times before entering lockout, but the exact count varies by model. Refer to the specific furnace manual for the exact retry limit.

Is It Safe To Reset The Furnace And Try Again?

Resetting is safe if the underlying issue is not a gas leak and the area is ventilated. If a gas odor is present or a leak is suspected, avoid resetting and contact a professional.

Resources And Manuals

OEM manuals and wiring diagrams aid accurate diagnostics. Visit the Atwood/RV Appliances support pages or authorized parts suppliers for model-specific documentation. When in doubt, rely on certified RV technicians for gas appliance repairs.

Key Takeaway: The Atwood furnace ignition lockout fault protects against unsafe conditions but usually stems from fixable issues like low propane, dirty flame sensors, faulty igniters, or venting problems. Systematic diagnostics, safety-first procedures, and preventive maintenance restore reliable operation and reduce the chance of repeat lockouts.