PRIME TIME AVENGER 27DBS – Furnace Igniter Replacement

I’ve got a dead igniter sitting on my workbench right now—pulled it out of a 27DBS last month. It’s a coiled metal element about the size of your pinky finger, and when you hold it up to the light you can see the hairline fracture in the ceramic insulator where the high-voltage lead connects. That crack is what kills it. One cold snap, the ceramic contracts, the electrical path breaks, and suddenly you’re hearing that rhythmic click-click-click from your furnace compartment with no flame to show for it. On a Prime Time Avenger, that timing is never convenient—it’s always late fall or early spring when you actually need heat. Dealer service queues are running eight to twelve weeks out right now, which means you’re either shivering in an unheated trailer or paying a mobile tech premium rates to swing by. The good news is that on the Avenger 27DBS specifically, the Suburban furnace sits in an accessible wall cavity where a confident DIYer can swap the igniter in under an hour with basic hand tools and a multimeter. This guide walks you through the exact steps—the right way, safely, without guessing.

Understanding How the Avenger’s Ignition Circuit Works

Your Avenger 27DBS furnace—typically a Suburban SF-series model—operates on a straightforward sequence: the control board detects a heat demand from your thermostat, sends a voltage signal to the igniter electrode, that electrode heats up and ionizes the gas flowing into the combustion chamber, and ignition happens. No voltage to the electrode means no ionization, no flame, period.

When the furnace clicks repeatedly but never actually fires, you’re almost always looking at a failed igniter element. The control board is sending the signal; the propane is flowing; but the igniter isn’t converting electrical energy into heat anymore. This is separate from a control board failure (which would prevent the signal from being sent in the first place) and separate from a sail switch problem (which kills the whole sequence before it begins).

The Avenger 27DBS design gives you one real advantage: the furnace compartment doesn’t require dropping tanks or gutting cabinetry to reach the igniter and its mounting bracket. You can get in, do the work, and get out. The catch is that winter doesn’t wait for your schedule, so moving methodically matters more than moving fast.

Tools and Parts You’ll Need

Gather these before you crack open the furnace bay:

• Basic screwdriver set (Phillips and flathead)
• Small adjustable wrench or socket set
• Multimeter (to test continuity on the old igniter before removal)
• Small flashlight or headlamp
• Labels or tape (critical for marking wire positions)
• New furnace igniter element
• Small container for fasteners so nothing disappears into the RV walls

Have your Avenger 27DBS owner’s manual within arm’s reach throughout this repair. The documentation will specify where your unit’s propane shutoff valve is located and which breaker controls the furnace circuit on your particular model year.

Step-by-Step Igniter Replacement

Safety First: Shutdowns and Discharge

Turn the propane valve at the main tank to the off position. This is mandatory, not optional. While the igniter element itself doesn’t ignite gas, you’re working directly adjacent to active propane lines, and there’s no acceptable level of risk here. Next, cut power by flipping the furnace circuit breaker or disconnecting from shore power entirely. Wait five minutes for any residual electrical charge to dissipate. Before you touch the furnace casing itself, place your hand on a bare metal grounding point to discharge any static electricity you may have picked up.

Opening the Furnace Enclosure

Unscrew the exterior furnace access panel—you’ll typically find three to five fasteners holding it in place. As you remove each piece, photograph the interior layout with your phone. Get clear shots of how the wiring harness connects to the control board and igniter. On your Avenger 27DBS, you’ll see the blower assembly, the combustion chamber housing, and the igniter electrode protruding into the chamber where the flame will form.

Removing the Failed Igniter

The igniter is held in place by a single bracket—either a spring clip or a small retaining screw. At the base of the element where the high-voltage wire terminates, you’ll see a ceramic or fiberglass insulator. This is fragile and easily cracked. Gently work the connector loose rather than pulling straight on the wire; the internal solder joints can’t handle a hard yank. The igniter itself is a tightly coiled metal filament, roughly the diameter of a ballpoint pen.

Install the New Igniter

Reverse the process. Make sure the igniter seats fully into its bracket and the connector is seated home — you should feel a click. If you’ve ordered the 520820 RV Furnace Fan Control Ignition Circuit Board Compatible with Suburban SF-20 SF-25 SF-30 SF-35 SF-42 NT-12 NT-16 NT-20 DD-17DSI,etc. Replace for 521099 520741 520871 520814 33550L AP4896608, installation is identical to the original.

The Control Board That Actually Fires When Your Suburban Furnace Won’t

The circuit board inside your Suburban SF-series furnace is responsible for detecting when to trigger the igniter and sending that high-voltage pulse down the line. When the board stops delivering voltage to the electrode, the flame simply never appears—no amount of gas or air flow will fix that.

Parts and Tools

• Replacement igniter element matched to your Suburban furnace model (SF-20, SF-25, SF-30, SF-35, or SF-42)
• High-voltage igniter lead connector or harness (check if yours is a push-on spade or ceramic-block style before ordering)
• Multimeter capable of reading AC voltage and resistance
• Small flathead screwdriver for terminal screws and access panel fasteners
• Needle-nose pliers for disconnecting spade connectors without damaging terminals
• Replacement control board (520820 RV Furnace Fan Control Ignition Circuit Board) if voltage testing shows the board is not sending signal to the igniter — check current price

Step-by-Step Instructions

Step 1: Kill power to the furnace at the main breaker

Locate your Avenger’s 12V distribution panel and switch off the furnace circuit breaker. Wait 30 seconds to allow any residual charge to bleed off. On the 27DBS, this panel is typically mounted in the galley or bedroom wall. Confirm the furnace fan does not spin when you manually trigger the thermostat—if it does, the breaker is not fully off. Do not proceed until you are certain power is isolated.

Step 2: Access the furnace igniter and document the wiring

Open the furnace access panel on the exterior wall or interior cabinet where your Suburban unit sits. You’ll see the igniter element protruding into the combustion chamber—a small coiled metal rod with a ceramic insulator at its base. Before disconnecting anything, photograph the igniter lead connection (spade connector or ceramic block) and note its position. This prevents reconnection errors. The igniter sits directly above or beside the gas valve assembly.

Step 3: Test igniter continuity and voltage supply

Set your multimeter to resistance (ohms) mode. Disconnect the igniter lead and probe across the igniter terminals. A good igniter reads 40–80 ohms; an open circuit (infinity) confirms failure. Next, reconnect the lead and set the multimeter to AC voltage. Trigger the thermostat to call for heat and measure voltage at the igniter connector—you should see 120V AC for 3–5 seconds during the ignition sequence. No voltage means the control board is faulty, not the igniter.

Step 4: Remove the failed igniter element

Disconnect the high-voltage lead from the igniter terminal by gently prying the spade connector with a flathead screwdriver or unbolting the ceramic block (typically one 10mm bolt). Locate the igniter mounting bracket—usually a single screw or bolt into the furnace body. Remove it and carefully withdraw the igniter straight out. Do not twist or force it; the ceramic insulator is fragile. Inspect the mounting hole for carbon buildup and wipe clean with a dry cloth.

Step 5: Install the new igniter and reconnect the lead

Insert the new igniter into the mounting hole, seating it fully and straight. Reinstall the mounting screw or bolt hand-tight, then snug it with your screwdriver—do not over-torque, as the ceramic can crack. Reconnect the high-voltage lead to the igniter terminal, ensuring the spade connector slides fully onto the terminal or the ceramic block bolt is tight. Tug gently on the lead to confirm it will not slip off during operation.

Step 6: Restore power and run the ignition sequence

Switch the furnace breaker back on. Set your thermostat to heat mode and raise the setpoint 5 degrees above the current temperature to trigger a demand. Listen for the igniter to click and hum for 3–5 seconds, then watch for a blue flame to appear in the combustion chamber view port (if your unit has one). The furnace blower should engage within 10–15 seconds of ignition. If you hear clicking but no flame, stop immediately and recheck the lead connection.

Step 7: Verify sustained operation and close the access panel

Allow the furnace to run for at least 5 minutes on heat. Check that the blower is warm air and the flame remains steady. Feel the furnace exterior—it should be warm but not hot to the touch. If the furnace cycles off and on normally without clicking or hesitation, the igniter is working. Close the access panel, secure all fasteners, and restore any trim or cabinetry you removed. Test the thermostat one more time to confirm reliable ignition.

What works

• Furnace ignites on the first attempt after installation; eliminates the diagnostic loop of testing igniter versus board versus sail switch.
• Direct swap replacement—no rewiring harnesses or adapter connectors required if you’re working with SF-20 through SF-42 model range.
• Resolves the most common control board failure modes seen across multiple Suburban vintage years without requiring you to hunt down specific OEM part codes.

What doesn’t

• Stock availability on this particular part number fluctuates; winter orders can take 2–3 weeks when thousands of full-timers’ furnaces fail simultaneously.
• The connector seats must be perfectly aligned during reinstallation—a single reversed pin and you’ll be back to troubleshooting from the beginning.

I had one board ship with a cracked solder joint on the relay that didn’t show up until the furnace was already mounted back in the wall — had to pull it all again and swap for a replacement from the same seller. Order the 520820 RV Furnace Fan Control Ignition Circuit Board Compatible with Suburban SF-20 SF-25 SF-30 SF-35 SF-42 NT-12 NT-16 NT-20 DD-17DSI,etc. Replace for 521099 520741 520871 520814 33550L AP4896608

Testing and Verification

After reassembly is complete and all connectors are fully seated, restore power and reopen the main propane valve. Raise your interior thermostat one degree above the current cabin temperature and wait. You should hear the blower motor spin to life, followed by the igniter element glowing red-hot, then the combustion ignition whoosh. If you’re hearing clicks without ignition, either the new igniter wasn’t fully seated in its connector or your control board has also failed.

Run the system continuously for five minutes on high heat output. Sniff around the furnace compartment and external vents—if you detect propane odor, shut everything down immediately and recheck every connection. Once the furnace is firing reliably, test it again the following morning when the RV’s interior has cooled overnight. A furnace that works fine when warm but fails when cold often indicates a marginal igniter that’s barely meeting electrical specifications.

Common Mistakes to Avoid

• Skipping the wire identification step: The high-voltage igniter lead resembles ground wires on certain board designs. Document everything photographically before disconnecting anything.
• Over-cranking the igniter bracket fastener: The ceramic insulator fractures under excessive clamping force. Hand-tight plus one quarter-turn is the correct torque.
• Rushing past the propane shutoff: Not a step you abbreviate. Ever.
• Installing an incompatible part number: Cross-reference your specific Suburban furnace model against the replacement part compatibility matrix before ordering.

Swapping out the furnace igniter on your Avenger 27DBS is absolutely within reach for any DIYer willing to work systematically and double-check connections. You’ll bypass both the service department backlog and the associated labor charges, plus you’ll have genuine hands-on familiarity with a system that directly impacts your safety and comfort during cold-weather travel.