Complete repair guide for the Winnebago Forza – 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 failure and prepare workspace
Begin by testing your furnace system to confirm the igniter electrode or control board is the culprit. Set your thermostat to heat mode and listen for the blower motor to engage; if you hear clicking but no ignition after 10-15 seconds, the igniter electrode has likely failed. If there’s no response at all, use your digital multimeter to test for 12V DC power at the furnace control board connectors—lack of voltage indicates a control board failure. Disconnect the negative battery terminal before beginning any work, then locate your furnace (typically mounted in the lower cabinet or storage compartment) and clear the surrounding area for safe access.
Step 2: Remove furnace cover and access components
Unbolt the furnace cover panel using a socket wrench or Phillips head screwdriver, depending on your Winnebago model year. Document the location of all wire connections by taking photos or creating a labeled diagram—this is critical for reassembly. Gently disconnect the main wiring harness from the furnace body and note the position of the propane feed line connection (typically a compression fitting you’ll turn counterclockwise, but do not disconnect the propane line itself yet unless replacing the entire unit).
Step 3: Test igniter electrode resistance and continuity
Locate the furnace igniter electrode, a ceramic or metal rod typically positioned near the combustion chamber burner. Using your digital multimeter set to the resistance (ohms) setting, probe both terminals of the igniter electrode—a properly functioning electrode should read between 40-100 ohms. If your reading is infinite (open circuit) or zero ohms (short circuit), the igniter electrode requires replacement. Disconnect the igniter electrode connector and carefully remove it from its mounting bracket by unbolting or unclipping as your model dictates.
Step 4: Replace igniter electrode with correct orientation
Install the new furnace igniter electrode into the mounting bracket, ensuring the ceramic insulator faces the combustion chamber and the metal tip aligns exactly with the burner assembly (typically 1/8 inch gap). Secure the electrode bracket bolt to approximately 12-15 inch-pounds of torque using a calibrated wrench to avoid cracking the ceramic. Reconnect the igniter electrode connector, verifying the connection clicks firmly into place with no visible corrosion on the terminals.
Step 5: Remove and replace the control board
Identify the furnace circuit board (control board), a rectangular circuit board typically mounted on the furnace side panel with multiple colored wires soldered or connected via terminal blocks. Take a final photo of all wire positions before proceeding. Carefully unsolder or disconnect each wire using your reference photos, then remove the mounting bolts (typically 2-3 Phillips screws) securing the old board to the furnace chassis. Install the new furnace circuit board in the identical orientation, reconnect all wires to their original positions matching your color-coded diagram, and ensure all solder joints are clean and secure—cold solder joints are a common cause of intermittent furnace failures.
Step 6: Verify switch operation and reconnect systems
Before reassembling, manually test the furnace sail switch (the safety switch that ensures airflow before ignition) by gently obstructing and releasing the sail damper—you should hear an audible click. Check that your high-limit switch (a thermal safety cutoff, usually red or orange-colored) moves freely and isn’t stuck in the tripped position. Reconnect the main wiring harness to the furnace body, then reconnect your negative battery terminal and prepare to test the system.
Step 7: Test furnace operation and verify ignition sequence
Set your thermostat to heat mode and listen carefully for the complete ignition sequence: the blower motor should activate first (you’ll hear the 12V DC fan spin), followed by a clicking sound as the igniter electrode sparks (approximately 30 seconds), and finally the whoosh of propane ignition. Using your Propane/CO combo detector alarm held near the furnace, verify there are no gas leaks or carbon monoxide present—the detector should show zero ppm CO. Allow the furnace to run for 5-10 minutes, confirming consistent heat output and that the high-limit switch doesn’t trip prematurely; if all systems function correctly and no alarms trigger, your furnace repair is complete.