Tiffin Allegro Bus – Furnace Igniter & Control Board Replacement

Most of the service calls I get aren’t emergencies — they’re deferred maintenance that finally gave up. The owner noticed something off weeks ago, ignored it, and now they’re calling me from a campground two states from home. Nine times out of ten, this repair could have been done for a fraction of the cost if they’d caught it early. With the Tiffin Allegro Bus furnace, the warning signs are almost always there first — a furnace that clicks but won’t light, one that runs the blower without producing heat, or a unit that trips out after a few minutes — and what starts as a failing igniter or a flaky control board becomes a full no-heat situation the moment temperatures drop and the system finally gives out for good. I’ve done this exact repair in muddy campground hookup pads, gravel driveways, and Walmart parking lots, so whether you’re tackling it yourself or just trying to understand what your technician is telling you, this guide gives you the straight story on how the repair actually gets done.

The Igniter That Actually Lights on the First Call — Suburban SF-Series

The igniter electrode is where most Allegro Bus furnace failures start — it clicks, sparks weakly, or doesn’t spark at all, leaving you with a blower running cold air and a dead thermostat. Replace the probe assembly and the control board will actually have something to work with.

What works

• Furnace fires reliably on the first attempt after installation — no more four or five ignition cycles before flame catches.
• The electrode gap stays consistent across heating seasons; you’re not chasing a weak spark every time the temperature drops.
• Installation is straightforward — two bolts, one connector, and you’re done in under 20 minutes without breaking the whole burner assembly apart.

What doesn’t

• Aftermarket probes sometimes arrive with slightly loose crimping on the wire assembly — you need to tug-test it before installation or risk a connector that vibrates loose in three weeks.
• If your control board is actually failing (not just starved for a clean spark), replacing the igniter alone won’t save the repair — you’ll light up and immediately lose flame as the board cuts gas flow.

I once swapped an igniter on a customer’s rig and it still wouldn’t hold flame — turned out the control board was already on its way out and needed replacement too, which meant doubling back and explaining why the first $80 fix didn’t stick. Order 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 continuity on the control board with a multimeter before you assume the igniter is the whole story.

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