Thor Four Winds – Furnace Igniter & Control Board Replacement

Thor Four Winds – Furnace Igniter & Control Board Replacement

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Complete repair guide for the Thor Four Winds – Furnace Igniter & Control Board Replacement. Follow these steps to diagnose and fix the issue yourself.

Parts & Tools You’ll Need

Step 1: Diagnose Furnace Ignition Failure

Turn off the propane supply at the tank and disconnect the 12V power to your furnace system at the main RV breaker. Use your digital multimeter set to DC voltage to test the control board’s output terminals—you should read approximately 12V when the thermostat calls for heat. If voltage is absent or the igniter electrode shows no spark when manually bridging the ignition circuit, your igniter electrode or control board has failed and requires replacement.

Step 2: Remove Furnace Access Panels

Locate your Thor Four Winds furnace access panel, typically positioned on the exterior wall or in a basement cabinet area. Remove the 4-6 fastening screws using a Phillips head screwdriver and carefully pull the metal access cover away from the furnace housing. Document the wire connections with photos or a labeled diagram before proceeding, as you’ll need to reconnect these components precisely.

Step 3: Disconnect and Extract Control Board

Identify the furnace circuit board mounted on the furnace’s internal frame—it’s typically a green or tan PCB with multiple terminal connectors. Carefully disconnect all wire harnesses from the board by gently wiggling connectors side-to-side while pulling straight out; do not yank on wires. Note which color wires attach to which numbered terminals (typically 1-8), then remove the mounting bolts securing the board to the furnace frame and set the old board aside.

Step 4: Replace Igniter Electrode Assembly

Locate the igniter electrode protruding from the furnace combustion chamber—it appears as a thin ceramic or porcelain rod approximately 0.5 inches in diameter. Unscrew the single set screw or bolt securing the electrode mounting bracket, then carefully withdraw the electrode straight out from its pocket. Install the new furnace igniter electrode by reversing this process, ensuring the ceramic insulator sits flush in the mounting pocket and torque the retaining bolt to approximately 8-10 inch-pounds.

Step 5: Install New Furnace Control Board

Position your new furnace circuit board onto the furnace frame mounting points and secure it with the original bolts, hand-tightening first to ensure proper alignment. Reconnect all wire harnesses to their corresponding terminal positions using your photo documentation, pressing connectors firmly until they seat with an audible click. Verify that the sail switch connector (typically a 2-pin connector) and high-limit switch wiring are connected to the correct terminals as specified in your replacement board’s documentation.

Step 6: Reconnect Propane and Power Systems

Reinstall the furnace access panel and secure all fastening screws. Restore 12V DC power at the RV main breaker and slowly open the propane supply valve at the tank, allowing 30 seconds for gas to pressurize the line. Check all visible connections for any gaps or loose fittings, and inspect the propane/CO combo detector alarm to ensure it’s functioning and properly mounted within 10 feet of the furnace exhaust outlet.

Step 7: Test System Operation and Verify Safety

Set your RV thermostat to heat mode and activate the heating cycle, listening for the distinct clicking sound of ignition within 5-10 seconds followed by blower motor engagement. Use your digital multimeter to confirm 12V output at the igniter electrode terminals during the ignition cycle. Allow the furnace to run for at least 10 minutes, verify warm air flows from all interior vents, and confirm your propane/CO detector shows normal operation with no alarm activation—if any alarm sounds, immediately shut off propane and check for gas leaks.