Tiffin Open Road Allegro – Furnace Igniter & Control Board Replacement

You’ll hear two very different stories about furnace work on a Tiffin Open Road Allegro. Walk into a dealer service bay, and they’ll tell you that igniter and control board failures need to be diagnosed by factory-trained techs, that the labor alone will run into the hundreds, and that you’re better off just letting them handle it. Then you’ll find forum threads where owners swap part numbers and talk through the whole process like it’s routine maintenance. One of those narratives is protecting a service revenue stream. The other one is real. When you’re living fulltime in your rig, the math shifts immediately — a mobile tech call or dealer appointment for a furnace failure costs several hundred dollars before any parts even get ordered, but once you understand how your Suburban or Atwood furnace actually fires (thermostat signal → sail switch → igniter sequence → flame detection), the repair becomes something you can genuinely handle yourself. A failed igniter or a dead control board will strand you without heat in conditions that range from uncomfortable to genuinely dangerous, but neither one requires a tech license to replace. What follows is based on hands-on experience with this exact repair — not just the steps, but why the system works the way it does, so you’re making informed decisions instead of just following a checklist. If your furnace is clicking without igniting, pushing cold air, or dead silent when you call for heat, this breakdown will help you figure out whether the igniter or control board is actually the problem, and exactly how to swap whichever part is failing.

The Igniter That Actually Lasts Through a Winter in a Tiffin Allegro

The igniter electrode is where most Suburban SF-35 furnace failures begin, and it’s the component that determines whether you’re staying warm or spending a miserable night shivering. When the igniter fails to spark, the control board never sees flame, the cycle shuts down on repeat — or won’t initiate at all.

Parts and Tools

• Replacement furnace igniter assembly matched to your Suburban or Atwood furnace model, with probe, electrode, and wire harness — check current price
• Replacement control board for your specific furnace model (Suburban or Atwood), with voltage and terminal configuration matching the original
• Multimeter capable of reading DC voltage and resistance (10-megohm minimum impedance for igniter testing)
• Small flashlight or headlamp for viewing the furnace interior and flame sensor location
• Needle-nose pliers and small screwdrivers (Phillips and flat-head) for terminal removal and fastener access
• Wire strippers and electrical tape for any harness repairs or terminal reconnection

Step-by-Step Instructions

Step 1: Kill power to the furnace and verify the thermostat is off

Locate your RV’s main 12V DC breaker panel and switch off the breaker feeding the furnace control board. Set your thermostat to OFF. Wait 30 seconds to allow any residual power to drain. This prevents accidental ignition attempts while you’re working and protects the control board from voltage spikes during disconnection. Do not skip this step—a live board can fire the igniter while your hands are near it.

Step 2: Access the furnace and photograph the wiring before disconnection

Open your RV’s furnace access panel (usually located in a floor cavity or cabinet near the water heater). Take clear photos of every wire connection to both the igniter and control board, including terminal positions and wire colors. This is your reference for reassembly. Note the exact position of the igniter probe relative to the burner and flame sensor. If you disconnect a wire and forget where it goes, you’ll have a non-firing furnace and no way to trace it back.

Step 3: Test the igniter with a multimeter to confirm failure

Set your multimeter to resistance (ohms) mode. Disconnect the igniter wire harness at the control board terminal. Probe the igniter leads directly. A good igniter reads between 4 and 14 ohms; anything above 20 ohms or an open circuit (infinity reading) means the igniter element is dead and needs replacement. If resistance is normal, the control board is likely the culprit. Document this reading before proceeding.

Step 4: Remove the failed igniter from the furnace burner assembly

Locate the igniter probe mounted near the burner flame area. It’s usually held by a single screw or clip. Carefully unscrew or unclip it without forcing—the ceramic insulator is fragile. Gently pull the igniter straight out and away from the burner. Do not bend the probe or twist the wire harness. Once free, disconnect the wire connector at the control board end. Keep the old igniter as a reference for terminal layout if needed.

Step 5: Install the replacement igniter and reconnect the harness

Position the new igniter probe in the same location as the original, typically 1/4 inch from the burner flame path and aligned with the flame sensor. Secure it with the original screw or clip, tightening firmly but not over-tight—you want it stable, not crushed. Reconnect the wire harness to the control board terminal, matching the wire colors and positions from your reference photos. Verify the connector is fully seated and the wires are not pinched.

Step 6: If replacing the control board, disconnect the old board and install the new one

If your multimeter test showed normal igniter resistance, the control board is the failure point. Disconnect all wires from the old board terminals, using your photos as a guide. Remove any mounting screws or clips holding the board in place. Install the new board in the same orientation and location. Reconnect each wire to its corresponding terminal on the new board, matching colors and positions exactly. Verify all connections are tight and no wires are trapped or pinched behind the board.

Step 7: Restore power and test the furnace ignition sequence

Switch the furnace breaker back on. Set your thermostat to HEAT and a temperature above the current cabin temperature. Listen for the sail switch click (air pressure switch), followed by a clicking or buzzing sound from the igniter for 3–5 seconds, then the whoosh of ignition and the burner flame. If you hear the igniter click but no flame appears, the igniter probe may be misaligned or the flame sensor may be dirty—clean the sensor with a soft cloth and retry. If nothing happens, recheck your wire connections against your photos.

What works

• Factory-matched part for SF-series units — installs directly into the existing mounting bracket with zero wiring changes or splicing required.
• The electrode spacing and geometry are calibrated correctly, so ignition happens on the first try after you install it — no gap adjustment or repositioning needed.
• The connector pins line up with your control board terminals cleanly, which means you won’t chase intermittent startup problems weeks later.

What doesn’t

• Marketplace sellers source units with hit-or-miss QC — ceramic housings can show stress cracks or connectors may have oxidation when they arrive, so unbox it immediately and check continuity with a multimeter before you commit to the install.
• Allegros built before 2010 may run a different control board generation where this part won’t seat without tweaking the mounting bracket slightly — cross-check your specific model year and board revision number against parts documentation first.

I second-guessed the part choice the first time I installed one because the connector felt slightly loose compared to the OEM part, but that turned out to be normal wear on the board side, not the new electrode. 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)