Complete repair guide for the Fleetwood Discovery – Furnace Igniter & Control Board Replacement. Follow these steps to diagnose and fix the issue yourself.
Parts & Tools You’ll Need
- Suburban RP-35Q 35,000 BTU/h RV Replacement Core for Suburban Furnace Series SF-35, SF-35Q, SF-42, SF-42Q, and SF-Q (2609A) — Suburban/Atwood RV furnace (replacement unit)
- Fit For Suburban RV Furnace Parts 232286,Single Probe Gas Furnace Igniters Electrode with Wire Assembly, Camper Furnace For Suburban 232286 Above 934701426 SF-20, SF-25, SF-30, SF-35 (SF Series) — Furnace igniter electrode
- DTAIR 33082 Sail Switch Replacement for Select Dometic Atwood RV Furnace(Pack of 2) — Furnace sail switch
- 520814 Rv Water Heater Module Board Ignition Control Circuit Board Compatible with Suburban Furnace SW4D, SW6D, SW6DE, SW12D, SW6DEM RV Water Heaters,Replace 520814 520820 520871 33550L (With lid) — Furnace circuit board / control board
- DTAIR 33082 Sail Switch Replacement for Select Dometic Atwood RV Furnace(Pack of 2) — Furnace high-limit switch
- Suburban 232684 RV Furnace 12v SF-Series DC Blower Motor, SF-35, SF-35F, SVF-35, SF-42, SF-42F OEM Caliber — Furnace blower motor (12V DC)
- RV Carbon Monoxide & Propane Gas Alarm, Briidea Dual LP/CO Detector with Separate LED Indicator Light, 100dB Loud Alarm, 12 VDC, Black — Propane/CO combo detector alarm
- FKM Pro Digital Multimeter Tester TRMS 6000 Counts,Smart Rechargeable Voltmeter 5″Color LCD,Auto-Ranging Automotive Multimeters,for AC/DC Current/Voltage,NCV,Ohm,Capacitance,Resistance,Continuity,Temp — Digital multimeter
Step 1: Diagnose Furnace Ignition Failure
Start by confirming the furnace won’t ignite by turning on the thermostat and listening for the blower motor to activate—if you hear the fan but no clicking or spark sound, the igniter electrode or control board is likely faulty. Use your digital multimeter set to DC voltage mode to test the control board’s output terminals; you should read approximately 12V DC when the thermostat calls for heat. If voltage is absent or extremely low, the control board requires replacement; if voltage is present but you hear no spark at the electrode, the igniter electrode itself is defective.
Step 2: Shut Down All Power and Propane
Turn off the propane supply at the tank valve by rotating it clockwise until snug, then switch off the RV’s 12V DC battery disconnect or battery master switch to eliminate electrical hazards. Wait 5 minutes to allow any residual pressure in the furnace lines to dissipate, and crack open a nearby window or door to ventilate any propane vapors that may be present in the RV.
Step 3: Access and Remove the Control Board
Locate the furnace control board mounted on the exterior or interior wall of your Fleetwood Discovery’s furnace unit—it’s typically a rectangular circuit board with 3-6 wire connectors attached. Before disconnecting anything, take a photo of the wire positions or label each connector with masking tape and a marker to ensure correct reinstallation. Disconnect all wire harnesses by gently pulling the plastic connector bodies straight out, then unbolt the control board from its mounting bracket using a 10mm wrench or socket, and set the old board aside.
Step 4: Replace Furnace Igniter Electrode Assembly
Locate the igniter electrode inside the furnace combustion chamber—it’s a small ceramic or metal rod positioned near the burner assembly and held in place by a single stainless steel bracket bolt. Unscrew the high-voltage wire terminal from the top of the old electrode, then remove the bracket bolt using a 7mm socket, and carefully slide out the defective electrode. Insert the new furnace igniter electrode into the bracket, ensuring the ceramic tip points toward the burner, hand-tighten the bracket bolt to approximately 4-6 foot-pounds (light resistance), and reattach the high-voltage wire terminal until snug.
Step 5: Install the New Furnace Circuit Board
Position the new furnace circuit board onto the mounting bracket and align the bolt holes, then insert and tighten the mounting bolts to 5-7 foot-pounds using a 10mm wrench. Reconnect all wire harnesses to their corresponding connectors—match each plug to your photos or labels, ensuring connectors click fully into place until you feel a positive detent. Verify that the high-voltage igniter wire is securely seated on the new board’s output terminal, as a loose connection here will prevent spark generation.
Step 6: Verify All Connections and Venting
Inspect the furnace burner assembly, sail switch, and high-limit switch to confirm all wiring remains intact and undamaged after your work. Check that the furnace exhaust vent pipe is clear of obstructions and that the intake air louver is unblocked—blockages can cause the high-limit switch to trip and shut down the furnace. Ensure all bracket bolts are tightened securely and that no loose wires are hanging near the burner or igniter area where heat could damage insulation.
Step 7: Test Furnace Function and Safety Systems
Restore power by switching on the 12V battery disconnect, then open the propane tank valve and wait 30 seconds for pressure to stabilize. Activate the thermostat to call for heat and listen for the blower to start within 5 seconds—you should hear a distinct clicking or buzzing sound as the igniter electrode sparks, followed by a soft whoosh as the burner ignites within 10-15 seconds. Allow the furnace to run for 2-3 minutes, verify warm air is flowing from the vents, then activate your Propane/CO combo detector alarm to confirm it reads zero ppm CO—if CO is detected above zero, shut down the furnace immediately and verify the exhaust vent is clear.