Complete repair guide for the Thor Freedom Traveler – 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 confirming whether your furnace has ignition issues (no spark at electrode) or control board failure (no power to igniter). Turn off propane at the tank and disconnect the 12V DC power from your RV battery. Locate your Thor Freedom Traveler’s furnace compartment—typically accessed from an exterior panel or interior cabinetry—and gather your digital multimeter, replacement igniter electrode, and control board to have everything within arm’s reach before disconnecting existing components.
Step 2: Remove Furnace Access Panels and Disconnect Power
Use a Phillips head screwdriver to remove the furnace’s outer access panels (usually 4-6 fasteners). Once exposed, locate and photograph the wiring harness connections to the control board and igniter electrode using your phone—this prevents reinstallation errors. Disconnect the 12V DC power connector from the control board and remove any ground wires secured with crimp terminals, labeling each connector with tape if your model doesn’t have color-coded connectors.
Step 3: Test Igniter Electrode for Electrical Continuity
Set your digital multimeter to the ohms (resistance) setting and probe both terminals of the igniter electrode. A healthy electrode should read between 3.5 and 5.5 megohms; readings exceeding 10 megohms or showing open circuit (∞) indicate the electrode has failed and requires replacement. If the electrode tests normal, the problem likely lies with your control board, allowing you to focus on that component instead.
Step 4: Remove Old Igniter Electrode and Control Board
The igniter electrode is typically held in place with a single screw or ceramic clip near the furnace combustion chamber. Carefully unscrew and remove it, noting its orientation relative to the burner tube—you’ll need to reinstall the new electrode in the identical position for proper spark gap (typically 3-4mm from the burner). Next, locate the control board mounted on the furnace frame and remove its mounting fasteners, sliding it out horizontally while noting cable routing.
Step 5: Install New Control Board with Proper Orientation
Slide your new furnace circuit board into the mounting brackets in the reverse order of removal, ensuring it sits flush and level with the furnace chassis. Reconnect the 12V DC power harness first—polarity matters with DC systems, so verify red connects to positive and black to negative by consulting your replacement board’s documentation. Then reattach all ground wires and any additional sensor harnesses (such as the sail switch and high-limit switch connectors) in their original positions as documented in your earlier photos.
Step 6: Install New Igniter Electrode with Correct Spark Gap
Position your new furnace igniter electrode into its mounting bracket, ensuring the tip is pointed directly at the burner tube opening. Secure the electrode fastener hand-tight, then use a feeler gauge or thin strip of cardstock to set the spark gap to exactly 3-4mm from the burner; this gap is critical for reliable ignition. Double-check that the electrode wire doesn’t contact any metal furnace components, as this would ground the spark and prevent ignition.
Step 7: Perform Power-Up Test and Verify Ignition Function
Reconnect your 12V DC battery, turn propane back on at the tank, and set your RV thermostat to heating mode at 70°F. Listen for the furnace fan to activate within 30 seconds, followed by a clicking spark sound at the igniter electrode for 10-15 seconds before the burner flame appears. If the spark is absent or ignition fails after 3 attempts, immediately shut off propane and recheck your control board and electrode connections; test with your digital multimeter if needed to confirm proper voltage (11.5-13.8V DC) at the igniter terminal.