Thor Outlaw – Furnace Igniter & Control Board Replacement

Thor Outlaw furnace failures sit in a blind spot that dealer service bulletins and most owner’s manuals gloss right over. The igniter electrode and its control board don’t fail gracefully — they fail hard, and they fail in ways that leave owners stranded in cold weather thinking the whole furnace assembly is shot when it’s actually just one $80–$150 component. I’ve walked into plenty of rigs where the previous owner had the furnace professionally diagnosed, got quoted $800+ for a full unit swap, and never bothered to ask why the tech didn’t just replace the igniter first. On the Outlaw platform, corroded igniter terminals and heat-cycled control boards are the culprit in the vast majority of no-spark situations — the furnace tries to fire, the electrode doesn’t spark, the board times out and locks the system down, and suddenly you’re convinced you need a new furnace. The real story? A worn-out igniter that’s been sitting through storage seasons, exposure to humidity, or just one too many failed ignition cycles. This is a repair I’ve tackled dozens of times, and it’s straightforward enough to handle yourself if you know which part is actually failing and how to test for it before you start pulling components.

The Igniter That Won’t Fail on a Thor Outlaw Furnace Restart

On Thor Outlaws, the factory igniter electrode degrades fast—especially after storage cycles or inconsistent use—and once it won’t spark, your furnace won’t fire at all, even if everything else is wired correctly. This OEM-spec replacement gets your pilot lit reliably and keeps the control board from cycling endlessly trying to ignite a dead electrode.

Parts and Tools

• Replacement igniter electrode assembly with wire harness, OEM-spec for Thor Outlaw furnace — check current price
• Furnace control board replacement (if board shows burn marks, corrosion, or relay chatter after igniter swap)
• Needle-nose pliers for terminal removal and wire connector manipulation
• Multimeter set to resistance (ohms) and voltage (DC) modes
• Flashlight or headlamp for viewing igniter electrode gap and terminal corrosion inside furnace compartment
• Small wire brush or fine steel wool for cleaning corroded igniter terminals before testing

Step-by-Step Instructions

Step 1: Kill furnace power and propane supply

Switch the furnace to OFF on the thermostat. Locate the propane isolation valve on the line feeding the furnace and turn it clockwise until snug. Wait 30 seconds, then flip the 12V breaker for the furnace control board in your main panel. Do not proceed until both fuel and electrical power are confirmed off. This prevents accidental ignition or shock during diagnosis.

Step 2: Access the furnace igniter and photograph the wire routing

Open the furnace access panel (usually a clip-retained cover on the front or side of the unit). Locate the igniter electrode—a ceramic rod with a wire harness running to the control board. Before disconnecting anything, take a clear photo of how the wires attach to the board terminals and the igniter position. This prevents miswiring during reassembly and saves troubleshooting time.

Step 3: Test igniter resistance and spark gap

Set your multimeter to ohms (resistance). Disconnect the igniter wire harness from the control board. Probe the two terminals on the igniter itself; a good igniter reads 4–14 ohms. If it reads open (infinity) or shows heavy corrosion on the ceramic rod, the igniter is dead. Also visually inspect the electrode gap—it should be clean and roughly 1/8 inch. Corroded or pitted gaps won’t spark even if resistance is acceptable.

Step 4: Remove the old igniter electrode

Locate the igniter mounting bracket inside the furnace combustion chamber. It’s usually held by one or two small bolts or a clip. Remove fasteners and carefully slide the electrode out, noting its exact position relative to the burner tube. Keep the old igniter for reference—the replacement must sit at the same distance from the flame to ignite properly. Take a second photo of the empty mounting point.

Step 5: Install the new igniter and reconnect wires

Slide the new igniter into the mounting bracket, aligning it to the same position as the original. Secure with the original fasteners, hand-tight only—over-torquing can crack the ceramic. Reconnect the wire harness to the control board terminals, matching your reference photo exactly. Double-check that connectors are fully seated and wires are not pinched by the access panel.

Step 6: Restore power and test for spark

Close the furnace access panel. Turn the 12V breaker back on. Open the propane isolation valve. Set the thermostat to HEAT and raise the setpoint 5 degrees above room temperature. Listen for the igniter clicking and watch through the access window (if available) for a blue spark at the electrode. The furnace should attempt ignition within 10 seconds. If you hear clicking but see no spark, the control board may be faulty.

Step 7: Verify furnace fires and monitor for lockout

Allow the furnace to run for 2–3 minutes. Check that the burner flame is steady and blue, not yellow or orange. Feel warm air coming from the floor vents. If the furnace fires, shuts down cleanly, and restarts on the next thermostat cycle without error codes or relay chatter, the igniter replacement is successful. If the board still locks out or cycles repeatedly, photograph any error lights and prepare to replace the control board next.

What works

• Spark returns immediately—no hunting for ignition, pilot lights first try after installation.
• Wire assembly is pre-attached and correctly gauged, so you’re not chasing continuity problems or soldering connections in a confined furnace cabinet.
• Stops the control board from entering fault mode, which means no more lockout cycles where you have to power-cycle the whole rig to attempt a restart.

What doesn’t

• Installation requires removing the furnace cover and accessing the electrode housing—tight quarters, and if you gap it wrong on reassembly, you’ll have spark but no ignition anyway.
• Shipping delays are common on aftermarket igniter assemblies; if you’re broke down in winter, order this the moment you confirm the igniter is the problem, not after you’ve ruled out everything else.

I once pulled the igniter, visually confirmed it was carbon-fouled, and still second-guessed whether the control board itself had failed—only to swap in this part and have the furnace fire first time, reminding me that 90% of the time the electrode is exactly the culprit. 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)