Thor Palazzo – Furnace Igniter & Control Board Replacement

“Drew, my Palazzo’s furnace keeps clicking but won’t actually fire. The blower kicks on when I turn up the thermostat, I can smell propane coming from the vents, but nothing ignites. Is this the igniter, or am I looking at a bigger problem?”

That question landed in my inbox last winter, and it’s the same one I hear every season from Palazzo owners who’ve watched their furnace go from reliable to completely unreliable. The pattern’s always identical: the spark electrode degrades until it can’t reliably light the fuel mixture, so you end up riding out cold nights on electric heat and crossing your fingers that a buyer won’t notice during a walkthrough. Here’s the thing nobody talks about until it’s time to sell — mechanical systems that have been nursed along instead of fixed sell for serious money less than a rig that’s been maintained, even if the rest of the interior looks showroom-fresh. I’ve walked through plenty of both kinds. The Thor Palazzo furnace develops failures in a specific sequence, and when the igniter or control board starts misfiring, you’ve got a job that sits squarely in the DIY-capable range — one that takes an afternoon and some basic tools. Get it working right, and you’ve got a furnace that catches immediately and runs without drama, which is exactly what a knowledgeable buyer is evaluating when they’re deciding whether this rig is actually ready to own.

Replacing the Igniter: When the Spark Electrode Stops Delivering Flame

Your Palazzo’s igniter is the component that generates the spark needed to catch the propane vapors — when this electrode weakens or burns out entirely, you end up with the thermostat calling for heat, the blower rotating, but no combustion happening inside the chamber. In the Suburban SF-series units found in the Palazzo, this igniter fails predictably and consistently, and it’s always my first diagnostic stop before I even consider pulling the control board.

Parts and Tools

• Replacement spark electrode igniter assembly with wire harness, matched to Suburban 232286 or equivalent for your Palazzo furnace model — check current price
• Furnace control board replacement (if igniter swap doesn’t restore ignition), specific to your Palazzo’s heating system
• Wire strippers and crimpers for reconnecting igniter harness terminals
• Multimeter set to measure DC voltage and resistance
• Small flashlight or headlamp for viewing the igniter electrode inside the furnace combustion chamber
• Screwdrivers (Phillips and flathead) for access panel and terminal fasteners

Step-by-Step Instructions

Step 1: Shut off propane and 12V power to the furnace

Turn the propane tank valve to the off position. Locate your Palazzo’s 12V battery disconnect or the dedicated furnace breaker in the coach panel and switch it off. Wait two minutes to allow any residual gas in the lines to clear. This prevents accidental ignition while you’re working and protects you from electrical shock when disconnecting harnesses.

Step 2: Access the furnace igniter and control board location

The Palazzo furnace is typically mounted in a basement compartment or under-floor cabinet. Open the access door and locate the control board (usually a rectangular module with wire terminals) and the igniter electrode assembly (a ceramic or metal probe with a wire running to the board). Take a clear photo of the wire connections before touching anything—this prevents reconnection errors later.

Step 3: Test the igniter electrode for spark and continuity

Restore 12V power briefly. Set your multimeter to resistance mode and touch the probes to the igniter terminals. A reading above 10 megohms or an open circuit confirms the electrode is dead. If the meter shows continuity, the igniter itself may be fine—the problem is likely the control board. Shut power off again before proceeding.

Step 4: Disconnect and remove the old igniter assembly

Locate the wire terminals connecting the igniter to the control board. Carefully pull the connector apart (do not yank the wires). If terminals are crimped, use wire strippers to carefully remove the old connector. Unscrew the igniter mounting bracket from the furnace combustion chamber wall—usually one or two small fasteners. Slide the electrode out and set it aside.

Step 5: Install the replacement igniter and reconnect terminals

Slide the new igniter electrode into the combustion chamber, aligning the mounting bracket with the original holes. Tighten fasteners snugly but do not over-torque—the ceramic probe breaks easily. Crimp or solder the wire terminals back onto the control board connectors, matching the polarity shown in your photo. Ensure all connections are tight and insulated.

Step 6: Restore power and test for spark and ignition

Turn 12V power back on and set the thermostat 5 degrees above the current temperature. Listen for the blower to start and watch for a visible spark at the electrode inside the combustion chamber (use your flashlight). You should hear a click-click-click spark sound for 3–5 seconds, then smell propane igniting. If spark occurs but no flame, the control board is likely faulty and needs replacement.

Step 7: Run a full heating cycle and verify stable operation

Allow the furnace to run for 10 minutes on high heat. The blower should stay on, the flame should remain steady, and the rig interior should warm gradually. Turn the thermostat down to trigger a shutdown cycle—the flame should extinguish cleanly and the blower should coast to a stop. If the furnace cycles normally without clicking, hesitation, or flame-out, the repair is complete.

What works

• Generates a strong, immediate spark on cold-start cycles without the sluggish ignition lag that comes with a worn electrode — you get the characteristic spark sound and propane smell right away, not after multiple failed attempts.
• Comes wired and ready to seat into the combustion chamber — no need to splice connectors in tight quarters or replace corroded terminals on the board-side harness connection.
• Fits SF-20 through SF-35 furnaces without modification — drops straight into position with no hunting for adapters or worrying about whether it’ll clear the sidewalls.

What doesn’t

• Retail availability swings wildly — sometimes it ships in under a week, other times it vanishes from stock for a month; if you’re cold and need heat immediately, a local service call to grab one from a tech’s inventory is faster than waiting for delivery.
• The attached wire harness requires deliberate routing through the furnace’s cable clips — I’ve seen loose assemblies rub against the metal shell during operation and develop shorts within a few weeks if you don’t secure it properly.

I once swapped one of these and the furnace still wouldn’t fire, which sent me down a two-hour rabbit hole testing the control board before I realized the problem was a loose sail switch, not the igniter — so make sure you check airflow activation first. Grab the 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) and test your blower and sail switch while you’ve got the system apart.

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