Few things are worse than a cold RV on a winter morning—especially in Iowa. If your RV furnace won’t ignite, blows cold air, or cycles without producing heat, you may not need major repairs. Many issues come down to power, airflow, or ignition problems, which you can check yourself.
This guide addresses the most common furnace issues RV owners encounter before contacting a certified technician. Use it to diagnose simple problems safely and save time (and freezing fingers).
1. Check Your Battery Voltage — The #1 Overlooked Issue
Your RV furnace relies on 12-volt DC power for:
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Ignition
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Blower motor
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Control board
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Safety sensors
If your battery is weak, the furnace may start the blower but fail mid-cycle.
Signs of low voltage:
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Furnace starts but won’t ignite
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Blower runs slowly or inconsistently
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Clicking sound but no flame
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Lights dim when furnace kicks on
Quick checks:
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Battery should read 12.4–12.8 volts (not plugged in)
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If plugged into shore power, converter should output 13.4–13.8 volts
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Check for loose or corroded battery terminals
👉 Pro Tip: Even brand-new RVs experience furnace issues when batteries dip below 12 volts.
2. Propane Flow Problems — Simple Fixes First
Your furnace needs proper propane pressure to ignite. If propane flow is restricted, the furnace will try to start but fail.
Common propane issues:
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Empty or low tank
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Regulator not functioning correctly
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Air trapped in the propane lines
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Excess Flow Valve triggered by opening the tank too quickly
Try this before panicking:
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Light a stove burner first — this confirms propane is reaching the RV
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Make sure your propane tank valve is fully open
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Switch to the second tank if you have a dual system
If your stovetop is weak or won’t stay lit, your regulator may be failing — a common winter issue.
3. Airflow Blockages — A Silent Furnace Killer
Your RV furnace has a safety system that shuts it down if it senses poor airflow or overheating.
Possible airflow restrictions:
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Blocked return air vents (dogs, pillows, storage bins)
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Closed supply vents
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Dust buildup in blower fan
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Furnace compartment filled with debris
What to check:
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Make sure ALL vents are open (closing vents can overheat the furnace)
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Inspect the return vent for dust buildup
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Remove anything stored near the furnace compartment
👉 If the furnace overheats, it will shut down until the sail switch resets.
4. Igniter or Burner Problems — What You Can Inspect Safely
If the furnace has power and propane, the next likely culprit is ignition failure.
Common symptoms:
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Clicking but no flame
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Furnace cycles repeatedly without heat
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Smell of propane before shutdown
Why this happens:
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Dirty igniter
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Misaligned igniter
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Carbon/soot buildup on the burner
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Rust or debris obstructing flame
User-safe check:
You can visually inspect the igniter area by removing the exterior furnace access panel.
Look for soot streaks, rust flakes, or insect nests around the burner.
⚠️ Do NOT disassemble the combustion chamber unless you are trained.
Incorrect reassembly can cause fire or carbon monoxide issues.
5. The Sail Switch — A $10 Part That Causes Big Problems
The sail switch is one of the most misunderstood furnace components. It must detect sufficient airflow before allowing propane to ignite.
What causes a failed sail switch:
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Dust or pet hair buildup
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Low battery voltage
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Weak blower motor
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Blocked vents
Symptoms:
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Furnace blower runs but never ignites
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System shuts down after 15–30 seconds
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Intermittent ignition that comes and goes
Sail switches often fail in winter because cold air makes the blower work harder.
6. Thermostat or Control Board Issues
If the furnace won’t even attempt to start:
Check your thermostat:
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Replace batteries (if it uses them)
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Make sure mode is set to “HEAT,” not “FAN”
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Ensure temperature is set above current room temp
If thermostat is fine, the control board may be at fault — especially if:
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No blower starts
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Furnace starts then dies instantly
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You hear no clicks or fan movement at all
7. When to Call a Certified RV Technician
If you’ve checked the basics and your furnace still won’t run, it’s time for a trained professional. Modern RV furnaces involve:
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High-temperature combustion
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Propane delivery systems
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CO safety mechanisms
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Electrical circuits and sensors
A certified tech can safely diagnose:
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Faulty control boards
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Damaged igniters
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Blocked burners
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Cracked heat exchangers (a serious CO risk)
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Failing blower motors
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Regulator pressure issues
Trying to force a furnace to run when something is wrong can create a fire hazard, CO leaks, or expensive damage.
MilTech RV Furnace Diagnostic — We Come to You
Don’t sit in a cold RV trying to troubleshoot for hours.
MilTech RV offers full furnace diagnostics, including:
✔ Voltage testing
✔ Ignition system inspection
✔ Burner and soot evaluation
✔ Airflow and vent checks
✔ Propane pressure testing
✔ Thermostat and control board diagnostics
✔ Safety checks and CO monitoring
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