Complete repair guide for the Coachmen Mirada – 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 turning on your RV furnace and listening for the blower motor to activate—if you hear the fan but smell no propane ignition attempt, the igniter electrode is likely faulty. Use your digital multimeter set to resistance mode to test the igniter electrode terminals; a reading above 10 ohms or an open circuit indicates electrode failure. If the blower runs but cuts off after 15-20 seconds without ignition, the sail switch or control board may be preventing proper operation—check the sail switch manually to ensure it moves freely when the blower activates.
Step 2: Shut Down Power and Propane Supply
Turn off the furnace at the thermostat and switch off the main 12V DC breaker on your RV’s electrical panel to prevent accidental ignition during removal. Locate your propane shut-off valve (typically near the propane tank or at the appliance inlet) and turn it fully clockwise until resistance is felt; verify no propane smell emanates from the furnace area for at least 30 seconds. Wait 5 minutes with all systems off to allow residual gas to dissipate safely before proceeding.
Step 3: Remove Furnace Access Panel and Components
Unbolt the furnace lower access panel (typically 4-6 bolts) and set it aside to expose the igniter electrode, sail switch, and control board mounted on the heat exchanger assembly. Disconnect the two-pin ceramic connector from the igniter electrode by gently pulling straight outward—do not twist or force, as the ceramic can crack. Take a photo of the control board wiring before disconnecting anything to reference during reassembly.
Step 4: Replace the Furnace Igniter Electrode
Locate the single bolt or clip securing the igniter electrode assembly (usually mounted near the burner tube) and remove it completely. Slide the old electrode out and insert the replacement furnace igniter electrode at the same angle and depth—it should sit 1/8 inch to 1/4 inch away from the burner orifice. Reconnect the ceramic two-pin connector firmly until you hear a click, ensuring a secure fit that prevents arcing.
Step 5: Install New Furnace Control Board
Disconnect the old furnace circuit board by unbolting it from its mounting bracket and carefully unplugging all attached connectors (typically 3-5 connectors for igniter, sail switch, thermostat, and blower motor). Note the color-coded wire positions or take detailed photos before removal. Mount the new furnace control board in the same orientation, reattach all connectors in their original positions by matching colors and terminal labels, and secure the board with its mounting bolts hand-tight, then final-tighten with a wrench to 6-8 foot-pounds.
Step 6: Verify Sail Switch and High-Limit Operation
Manually press the furnace sail switch to confirm it clicks audibly and moves freely without sticking—if resistance is high or movement is sluggish, replace the furnace sail switch to ensure proper blower activation detection. Check that the furnace high-limit switch (a bi-metal safety device typically mounted on the heat exchanger) is clean and unobstructed; clean any dust with a soft brush and confirm it resets fully when cooled. Reinstall the access panel with all bolts snug to 10-12 foot-pounds, ensuring no gaps remain that could leak propane odor.
Step 7: Test Ignition and Monitor System Performance
Turn the main 12V breaker back on and open the propane supply valve fully; set your RV thermostat 5 degrees above the current interior temperature to trigger furnace startup. Listen for the blower motor to engage within 5 seconds, followed by a clicking sound (igniter firing) within 10-15 seconds, and smell for a faint propane odor confirming ignition—flames should appear in the burner tube. Run the furnace for 15 minutes while monitoring the outlet temperature (should reach 130-150°F) and verify the Propane/CO combo detector alarm does not sound; if any anomalies occur, turn off the furnace immediately and recheck all connections.