Complete repair guide for the Entegra Cornerstone – 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 listening for the distinctive clicking sound when you turn on the furnace—if you hear rapid clicking but no ignition flame appears within 10 seconds, your igniter electrode is likely faulty. Use your digital multimeter set to the ohms setting to test the igniter electrode’s resistance; it should read between 4-14 ohms when cold. If the meter shows infinite resistance or no continuity, or if you see a cracked/corroded electrode tip, you’ve confirmed the igniter needs replacement.
Step 2: Turn Off Power and Propane Supply
Switch off the furnace at the thermostat and flip the 12V DC breaker on your RV’s electrical panel to cut all power to the furnace circuit. Locate your propane tank valve—typically mounted on the exterior of your Entegra Cornerstone—and turn it fully clockwise to shut off gas flow completely. Wait 2-3 minutes to allow any residual propane in the lines to dissipate before proceeding with any work.
Step 3: Access and Remove Furnace Assembly
Open your RV’s furnace access panel, typically located behind a removable trim piece in your galley or bedroom area, using a Phillips screwdriver. Locate the quick-disconnect propane line coupling and disconnect it by gently twisting counterclockwise, then disconnect the 12V wire harness from the control board by pressing the release tab and pulling straight out. Remove the four mounting bolts (usually 3/8-inch) that secure the furnace unit to the RV frame and carefully slide the entire furnace assembly out far enough to access the internal components.
Step 4: Replace Igniter Electrode Assembly
Locate the igniter electrode at the bottom-front of the furnace combustion chamber—it’s a small ceramic-tipped rod approximately 1.5 inches long. Disconnect the single wire spade connector from the electrode terminal and unscrew the mounting bracket bolt (typically 1/4-inch), then slide the old electrode out of its holder. Install the new furnace igniter electrode by reversing this process, ensuring the ceramic tip sits at the correct 1/8-inch distance from the burner flame pattern, then reconnect the spade connector firmly.
Step 5: Inspect and Replace Control Board
With the furnace still accessible, examine the furnace circuit board for visible damage such as burnt components, corrosion, or loose solder joints—any of these indicate a failed board. Disconnect all wire harnesses from the control board by noting their positions (take a photo for reference), then remove the mounting screws securing the board to the furnace frame. Install the new furnace circuit board in the same orientation, reconnect all wire harnesses to their original positions matching your reference photo, and ensure each connector clicks fully into place.
Step 6: Reinstall Furnace and Verify Connections
Carefully slide the furnace assembly back into its wall cavity, aligning the mounting bolt holes with the RV frame. Reinstall the four mounting bolts and tighten them to approximately 15-20 foot-pounds of torque to prevent vibration rattles without over-tightening. Reconnect the 12V wire harness to the control board until you hear a definitive click, then reattach the propane quick-disconnect coupling by twisting clockwise until snug (do not over-tighten—hand-tight plus 1/4 turn is correct).
Step 7: Test Ignition and Monitor Safe Operation
Turn the propane tank valve counterclockwise to restore gas flow, then switch on the 12V breaker and activate the furnace via your thermostat. Listen for the igniter electrode’s clicking for 10-15 seconds followed by a reliable “whoosh” as the burner ignites, producing a steady blue flame—if flame appears within 20 seconds, the replacement was successful. Run the furnace for 10 minutes while monitoring for any propane odor using your nose and checking the Propane/CO combo detector alarm to confirm it reads normal levels; if the detector alarms or you smell gas, shut off the furnace immediately and inspect the propane connection for leaks using soapy water.