Complete repair guide for the Tiffin Zephyr – 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 the Furnace Malfunction
Start by identifying whether you’re dealing with an igniter electrode failure or control board issue by listening for the characteristic clicking sound when the thermostat calls for heat—a rapid clicking indicates igniter problems, while complete silence suggests a control board failure. Use your digital multimeter set to DC voltage to test the 12V output at the control board terminals; you should read between 10.5-14V. Document which symptoms you’re observing and visually inspect the igniter electrode for cracks, corrosion, or carbon buildup that would necessitate replacement.
Step 2: Disconnect Power and Isolate Propane
Turn off the RV’s main 12V DC battery disconnect switch and shut the propane supply valve at the tank before beginning any work on the furnace assembly. Wait at least 5 minutes to allow residual pressure in the propane lines to dissipate safely. Verify the propane valve is fully closed by turning the handle perpendicular to the pipe—this prevents accidental gas release during disassembly.
Step 3: Remove the Furnace Access Panel
Locate the furnace unit typically mounted in the basement or underbelly compartment of your Tiffin Zephyr and remove the access panel by unscrewing the 4-6 Phillips head fasteners along its perimeter. Take a photo of the internal wiring configuration before disconnecting anything—this serves as your reassembly reference. Gently pull the access panel away from the furnace body and set aside in a safe location.
Step 4: Replace the Igniter Electrode Assembly
Locate the igniter electrode mounted near the burner chamber—it’s a ceramic-tipped probe approximately 2-3 inches long with a high-voltage wire attached. Disconnect the high-voltage wire by gently twisting the connector counterclockwise, then remove the single mounting screw holding the electrode bracket to the furnace frame. Insert the new furnace igniter electrode into the same mounting position, ensuring it sits at the correct angle (typically 1/8 inch from the burner orifice), secure with the mounting screw, and reconnect the high-voltage wire firmly until you hear a click.
Step 5: Remove and Install the Control Board
Disconnect all wire terminals from the old furnace circuit board by photographing their positions first, then carefully pulling each connector straight out—forcing them can bend the pins. Remove the 2-3 mounting screws securing the board to the furnace chassis, slide the old board out, and install the new furnace circuit board by reversing these steps. Match each wire connector to its corresponding terminal using your reference photo, ensuring connections are fully seated with no exposed pins.
Step 6: Verify Sail Switch and High-Limit Engagement
Check that the furnace sail switch—a hinged metal flapper that detects air flow—moves freely without sticking and returns to its resting position when manually deflected. Test the high-limit switch (a safety thermostat typically set at 190-200°F) by manually pressing its reset button if it’s triggered; you should hear a soft click when it resets. Ensure both switches are properly seated in their mounting brackets with secure electrical connections.
Step 7: Power On and Test Complete System Operation
Reconnect the RV’s 12V battery switch and reopen the propane valve at the tank, then set your thermostat to heat mode and turn it up 5 degrees above the current interior temperature. Listen for the blower motor to activate within 30 seconds, followed by the igniter electrode clicking for 5-10 seconds before the burner ignites with a soft “whoosh” sound. Allow the furnace to run for 5 minutes, verify warm air is flowing from the vents using your hand, confirm the Propane/CO combo detector alarm doesn’t sound, and monitor that the furnace cycles off when reaching the set temperature.