RV Furnace Won’t Ignite: Troubleshooting Causes, Fixes, and Safety Tips

When an RV furnace won’t ignite, the problem is usually a simple issue with power, propane, airflow, or ignition controls. This guide explains how the system works, shows fast checks that solve most no-ignite issues, and outlines step-by-step diagnostics with safety in mind. Use it to get heat back quickly and know when to call a pro.

Meta Description: RV furnace won’t ignite? Learn fast checks, detailed troubleshooting, common causes, and safe fixes for Suburban and Atwood/Dometic propane furnaces, including sail switch, ignition, and propane pressure tips.

Quick Safety Check Before Troubleshooting

Safety comes first whenever working with propane and combustion appliances. Before any diagnostic steps, review these precautions to protect people and equipment.

• If you smell propane, shut off the tank valve, extinguish flames, ventilate, and leave the RV. Do not operate electrical switches. Call a pro if the smell persists.
• Verify carbon monoxide protection. Test CO and LP gas alarms. Replace units older than 5–7 years per manufacturer guidance.
• Work in a ventilated area. Keep pets and children away. Avoid sparks when propane lines are open.
• Disconnect 12V power and close the propane valve before removing the furnace or opening the gas train.
• Use leak detection solution (or soapy water) to check joints after any gas work. Never use an open flame.

How An RV Propane Furnace Works (And Why It Won’t Ignite)

Most RV furnaces (Suburban, Atwood/Dometic) are 12V DC, forced-air propane heaters. Understanding the ignition sequence helps pinpoint where the failure occurs.

• Thermostat calls for heat and sends a 12V signal to the control board.
• Blower starts a pre-purge (typically 15–30 seconds) to clear the combustion chamber.
• Airflow closes the sail switch (air-proving switch). If it doesn’t close, ignition is blocked.
• The control board energizes the igniter (spark) and opens the gas valve to the burner.
• Flame lights. A flame sensor (often the same electrode) confirms flame via microamp “flame rectification.”
• If no flame is detected, the board retries. After several failed attempts, it locks out for safety.

No-ignite causes typically cluster around four areas: insufficient 12V power, low/blocked propane supply, airflow faults (sail switch/ducting), or ignition/flame-sense problems.

Fast Checks When An RV Furnace Won’t Ignite

These quick checks resolve many “RV furnace not igniting” complaints without tools. Perform them in order.

• Thermostat: Set heat mode and raise setpoint 5–10°F above room temperature. Confirm furnace is selected if using a multi-zone/digital thermostat.
• Battery voltage: Ensure house batteries are charged. Many boards need >10.8–11.5V under load at the furnace. Connect shore power if possible.
• Propane: Verify LP level and that the tank valve is fully open. If the RV sat a while, purge air by lighting a stove burner for a minute.
• Regulator position: If you have an automatic changeover, ensure the active side has fuel and the lever points correctly.
• Airflow: Open supply registers, clear return air grills, and inspect exterior intake/exhaust for insect nests or obstructions.
• Power cycle: Turn the thermostat off for 60 seconds, then back on. Some boards reset lockout this way.

Detailed Troubleshooting Steps

Step 1: Confirm 12V Power And Thermostat

Low voltage is a top reason a furnace blower runs but the gas valve never opens. Measure voltage directly at the furnace.

• With a digital multimeter, check DC voltage at the furnace input during startup. Target: ≥12.0V under load; many boards drop out near 10.5–11.0V.
• If voltage is low, charge batteries, check connections, fuses, and grounds. Inspect the battery cutoff switch and converter output (13.4–13.8V typical on shore power).
• Bypass-test the thermostat: carefully jump the furnace’s control wires per the service manual to see if the unit starts, confirming a thermostat/control wiring issue. Do not short random wires; consult your wiring diagram.

Step 2: Verify Propane Supply And Pressure

A furnace may spark but not light if LP pressure is low or air remains in the lines. Check supply and regulator health.

• Light multiple stove burners for 60–90 seconds to purge air. Try the furnace again.
• Ensure the two-stage regulator vent is clear and facing down. Replace regulators older than ~10 years or if they exhibit wandering pressure.
• Use a manometer on the test port: Static ≈ 11” W.C. and Under load ≥ 10.5” W.C. while the furnace and another appliance run. If low, replace the regulator or address tank/valve issues.

Step 3: Observe The Ignition Cycle

Watching and listening tells where the sequence fails. Take notes for each attempt.

• Blower runs? If not, check fuses, motor, and 12V feed.
• After pre-purge, do you hear repeated ticking (spark) and smell faint propane? If there’s spark and gas but no flame, suspect igniter gap, burner, or airflow.
• No ticking and no gas sound often points to the sail switch not proving or the control board not energizing.
• Flame lights then goes out after a few seconds? That usually indicates flame-sense signal loss or a grounding issue.

Step 4: Sail Switch And Airflow Issues

The sail switch must close to allow ignition. Weak airflow from low voltage, obstructions, or a sticky switch prevents closure.

• Inspect return and supply ducts for blockages, crushed hoses, or closed registers. A blocked system overheats and fails to light or cycles off.
• Check the blower wheel for lint, pet hair, or debris. Clean carefully; maintain blade balance.
• Test the sail switch continuity while running (per manual). Replace if intermittent. Ensure wires and spade connectors are snug.

Step 5: Limit Switch And Overheat Protection

The high-limit switch opens if the heat exchanger overheats. An open limit can stop or abort ignition.

• Verify continuity across the limit switch at ambient temperature. If open when cool, replace it.
• If the limit opens mid-cycle, improve airflow: open registers, straighten ducts, clear returns, and confirm blower performance.
• Inspect the furnace for signs of heat damage and verify correct BTU model for the duct layout.

Step 6: Igniter, Spark Gap, And Flame Sensor

Most RV furnaces use a spark electrode that also senses flame. Poor gap or contamination can prevent lighting or flame recognition.

• Remove power and access the burner assembly. Clean the electrode with fine abrasive (do not sand excessively).
• Set spark gap per the service manual (commonly ~1/8 inch or 3 mm). Confirm the tip is positioned in the gas stream.
• Clean and tighten grounds between the burner, control board, and chassis. Flame sensing relies on a solid ground path.
• Inspect the ignition wire for cracks and carbon tracking. Replace brittle or damaged leads.

Step 7: Gas Valve, Orifice, And Burner

If the valve opens but ignition fails, check the orifice and burner for contamination and proper flame.

• Remove and visually inspect the burner and orifice. Look for rust flakes or insect webs, especially from spiders.
• Clean with compressed air; do not enlarge the orifice. Replace parts if damaged.
• Confirm the gas valve receives 12V during ignition. If it does and no gas flows, the valve may be faulty. Verify LP pressure first.

Step 8: Control Board, Connectors, And Diagnostics

Control boards manage timing, spark, gas, and safety lockout. Intermittent boards often show up as random failures.

• Inspect the board for corrosion, heat damage, or cold solder joints. Reseat connectors and clean spades with contact cleaner.
• Many modern boards have LED diagnostics. Count blinks per the manual for fault codes and follow the decision tree.
• If in doubt, test with a known-good or high-quality replacement board (e.g., OEM or reputable aftermarket). Verify correct part number.

Step 9: Ducting, Exhaust, And Intake

Restricted intake or exhaust disrupts combustion and can cause no-ignite or flame-out.

• From the exterior, inspect concentric intake/exhaust or dual ports for nests and debris. Install bug screens designed for RV appliances.
• Ensure the coach’s interior ducting matches furnace requirements for minimum open register area.
• If installed in a tight cabinet, confirm adequate return air openings meet manufacturer specs.

Common Scenarios And Fixes

The table below matches symptoms with likely causes, quick tests, and fixes to speed up “RV furnace not igniting” diagnostics.

Tools And Specs Cheat Sheet

Having the right tools makes RV furnace troubleshooting safer and faster. Keep this kit and spec list on hand.

Brand-Specific Notes

Suburban and Atwood/Dometic furnaces share core concepts but differ in parts layout and diagnostics. Check the exact model for part numbers and settings.

• Suburban: Common models SF, NT. Often use a separate electrode assembly and robust heat exchangers. Access to sail and limit switches varies by cabinet orientation.
• Atwood/Dometic: Common models 8500, 8900 series. Many use an electrode that both ignites and senses flame. Some boards are more sensitive to ground quality.
• Diagnostics: Newer OEM or replacement boards may include an LED with blink codes. Keep the legend from the manual or board label accessible during testing.

Cold-Weather Tips To Prevent No-Ignite Issues

Extreme cold can expose weak components and fuel delivery issues. Preventive steps keep the furnace reliable during winter camping or travel.

• Keep batteries warm and charged. Cold reduces capacity and voltage. Use shore power, solar, or a generator to maintain charge.
• Protect the regulator from freezing moisture. Ensure the vent points down and is shielded from road spray.
• Use clean propane. Have tanks filled at reputable suppliers. Water or contaminants can impair regulator performance.
• Maintain airflow. Do not block returns with bedding or gear. Open enough registers to meet minimum airflow.
• Cycle the furnace periodically to keep components dry and ready, especially after storage.

Maintenance Schedule And Cost Guide

Routine care reduces “RV furnace won’t ignite” events and extends service life. Plan annual checks and budget for wear items.

• Every Trip: Test furnace operation, verify CO/LP alarms, inspect exterior intake/exhaust, confirm open registers.
• Seasonally: Clean return grills and ducts, check battery health, exercise the furnace under load for 15–30 minutes.
• Annually: Remove and clean burner/orifice, inspect electrode and set gap, clean grounds and connectors, test sail/limit switches.
• Every 5–10 Years: Replace the LP regulator; replace CO/LP alarms per manufacturer age limits.

Typical parts costs vary by model and brand.

• Sail switch: ~$20–$50
• Limit switch: ~$15–$40
• Igniter/electrode: ~$25–$70
• Control board: ~$100–$250
• Two-stage regulator: ~$35–$90

Labor at RV service centers commonly ranges from $120–$180 per hour. Complex access or ducting issues can add time. DIYers can save by performing cleaning, testing, and simple part swaps.

When To Call A Pro

Some furnace problems demand specialized tools or experience. Stop and seek help in these situations to avoid hazards and damage.

• Persistent gas smell, or failed leak checks on the LP system
• LP pressure outside 10.5–11.5” W.C. after regulator adjustments
• Cracked heat exchanger (risk of CO leaks into living space)
• Repeated lockouts after basic cleaning and part replacement
• Electrical issues beyond basic 12V checks or evidence of wiring damage

Local RV service centers, mobile technicians, and propane dealers can test regulators and pressure accurately. Consult manufacturer service locators via Suburban and Dometic.

Frequently Asked Questions

How Long Should The Blower Run Before Ignition?

Most units run a 15–30 second pre-purge before attempting ignition. If no flame, the board may try 2–3 more times. After multiple failed attempts, the system enters lockout and must be reset.

Why Does My RV Furnace Light And Then Go Out?

This points to flame-sense failure or overheating. Common causes include a dirty or misaligned electrode, poor ground, restricted airflow, or a weak flame from low LP pressure. Clean the electrode, confirm grounds, open registers, and verify pressure.

Can A Thermostat Cause A No-Ignite?

Yes. If the thermostat fails to send a steady heat call, the furnace will not start or may drop out. For simple two-wire thermostats, jumping the heat-call circuit (per the manual) can confirm a thermostat issue.

Is It Normal To Smell Propane During Start-Up?

A faint whiff outside near the exhaust during retries can occur, but strong or persistent odor is not normal. Shut off LP, ventilate, and leak-test connections. Do not continue attempting to light until the source is identified.

Will Low Battery Voltage Stop Ignition?

Yes. The blower may spin, but low voltage can prevent the gas valve from opening or the control board from maintaining spark/flame sense. Keep batteries above 12.0V under load and verify tight grounds.

Where Is The Sail Switch Located?

It’s typically mounted in the blower housing on the furnace, with a small paddle in the airflow stream. Access varies by model; some require removing the furnace. Consult the service manual for your unit.

How Do I Reset A Furnace After Lockout?

Turn the thermostat off for 30–60 seconds, then back on. Some models require cycling the 12V fuse or power. If lockouts persist, follow the troubleshooting steps to address the root cause.

What Does A Healthy Flame Look Like?

A proper flame is steady, mostly blue, and contained within the burner. Yellow tips indicate contamination or improper air/fuel mixing, often due to a dirty burner, low LP pressure, or blocked intake/exhaust.

Should I Install Bug Screens On Vents?

Yes, if they’re designed for RV appliances. They help prevent insect nests that block airflow. Choose screens that do not significantly restrict intake/exhaust and clean them regularly.

SEO Tips For Finding Parts And Manuals

When searching on Bing, include the brand and model in queries for better results. Sample queries that match common issues:

• “Suburban SF-30 furnace won’t ignite troubleshooting”
• “Atwood 8500 series RV furnace flame sensor gap”
• “RV furnace blower runs but no heat sail switch”
• “RV furnace propane pressure 11 inch water column manometer”
• “Dinosaur control board RV furnace LED codes”

Manufacturer support pages and RV forums often host PDFs and service bulletins that clarify model-specific tests. Always verify parts by serial and model number.

Step-By-Step Quick-Start Diagnostic Flow

Use this condensed checklist to rapidly isolate a no-ignite fault. Stop at any unsafe finding and correct before proceeding.

1. Set thermostat to heat and raise setpoint; confirm furnace selection on digital controllers.
2. Verify 12V supply at furnace during startup (≥12.0V). Charge batteries or fix connections as needed.
3. Check LP level; open tank; purge air by lighting stove burners; try furnace again.
4. Inspect exterior intake/exhaust, interior returns, and registers; clear obstructions.
5. Listen for spark. If no spark, test sail switch and limit switch continuity; check for board LED codes.
6. If spark present but no flame, measure LP pressure (11” W.C. static, ≥10.5” W.C. running) and clean the burner/orifice.
7. If flame lights then dies, clean/adjust electrode and grounds; verify ducting and limit switch behavior.
8. Reseat wiring harnesses; inspect the control board; consider replacement if intermittent after other fixes.

Key Takeaways For A Furnace That Won’t Ignite

Most problems are solvable with methodical checks of power, propane, airflow, and ignition. Keep batteries strong, maintain clean burners and good grounds, and ensure proper LP pressure to prevent issues.

• Power: Low 12V equals weak airflow and failed ignition. Verify under-load voltage.
• Propane: Purge air and keep pressure within spec. Replace aging regulators.
• Airflow: Clear returns and ducts; a stuck sail switch blocks ignition.
• Ignition: Correct electrode gap and clean grounds enable lighting and flame sense.
• Safety: If you smell gas or suspect a heat exchanger crack, stop and call a pro.

With these steps, RV owners can confidently troubleshoot a furnace that won’t ignite, restore heat faster, and maintain safe, reliable operation on the road.