RV Furnace Blowing Cold Air: Causes, Troubleshooting, and Solutions

When an RV furnace blows cold air, it disrupts comfort, especially during cool-weather adventures. This guide covers the most common reasons why an RV furnace may stop producing heat, step-by-step troubleshooting, and actionable solutions to restore cozy warmth inside your motorhome or trailer.

Common Causes Of An RV Furnace Blowing Cold Air

There are several reasons why your RV furnace might not deliver hot air. Identifying the root cause is essential for effective repair and preventing further issues on the road.

• Insufficient Propane Supply
• Electrical Power or Battery Problems
• Ignition or Pilot Light Failure
• Faulty Thermostat
• Furnace Component Malfunctions (Limit switch, Sail switch, Circuit board)
• Airflow Restrictions or Blockages
• Improper Furnace Settings

How An RV Furnace Works: A Quick Overview

An RV furnace relies on propane gas, 12V DC power, and proper ventilation. The process begins when the thermostat calls for heat, triggering the fan, igniter, and propane valve. Hot combustion air circulates through ducts, warming the living area.

If any component in this sequence malfunctions, the furnace may fail to heat the air—resulting in cold air from the vents.

Troubleshooting Steps For An RV Furnace Blowing Cold Air

Diagnosing why your RV furnace is blowing cold air requires a systematic approach. Follow these steps, checking each factor in turn.

Check The Thermostat

• Ensure the thermostat is switched to the “heat” setting.
• Set the temperature higher than the ambient temperature.
• Replace batteries if the thermostat is battery-powered.
• Inspect for loose wires or display errors.

Improper thermostat settings or malfunctions are a simple fix but often overlooked.

Verify Propane Supply

• Confirm propane tank levels and open the tank valve fully.
• Check for kinked, blocked, or frozen propane lines.
• Monitor other propane appliances for proper function.
• Inspect regulators and hoses for leaks or damage.

Low or interrupted propane supply is a leading culprit of cold air output and incomplete combustion.

Examine Electrical Power & Battery Voltage

• Test the RV battery voltage (should be >12 volts).
• Ensure connections to the furnace and fuse panel are secure.
• Check the fuses and circuit breakers assigned to the HVAC system.
• Plug the RV into shore power and observe if the furnace operates correctly.

Low 12V power can prevent the furnace igniter and blower from operating properly, resulting in a no-heat condition.

Inspect The Ignition System

• Listen for a clicking sound, indicating the igniter is sparking.
• Observe if the burner lights up (can look for a blue flame through the inspection port).
• Smell for unburned propane—if present, the gas valve is opening but ignition is failing.
• For older furnaces, ensure the pilot light is on.

Ignition or pilot light failure causes the fan to blow cold, unheated air through the vents.

Assess Key Furnace Components

Several internal parts can malfunction, each having a specific symptom:

• Limit Switch: Prevents the furnace from overheating. A faulty switch can shut off the burner.
• Sail Switch: Senses airflow. If stuck or dirty, it blocks the ignition sequence.
• Circuit Board: Controls the ignition and timing. Faults here may cause random heat loss.

Component failures often require professional diagnosis and repair or replacement parts.

Look For Airflow Blockages

• Ensure all interior and exterior vents are open and unobstructed.
• Clean return air grills and ducts regularly.
• Check for rodent nests or debris inside or around the furnace compartment.

Blocked airflow can cause overheat shutdowns or reduce heat output, causing perceived cold air even when the burner is functional.

When To Call A Professional

If after performing these steps your RV furnace continues to blow cold air, it may be time to consult a certified RV technician. Complex repairs involving the gas system or electronics should be conducted by professionals to ensure safety and compliance with RV standards.

Preventative Maintenance To Avoid Furnace Problems

Preventive steps help minimize the risk of a cold-blowing RV furnace and expensive repairs:

• Check and clean all vents regularly.
• Drain and inspect propane tanks and lines for leaks or obstructions.
• Test furnace operation before travel or seasonal use.
• Replace air filters and thermostat batteries as needed.
• Annual maintenance by an RV professional is highly recommended.

Common RV Furnace Models And Their Troubleshooting Characteristics

Different makes and models may have unique quirks. Understanding your furnace’s manufacturer instructions and error codes can simplify troubleshooting.

Model	Common Error Symptoms	Basic Troubleshooting Tip
Suburban NT-30SP	Intermittent ignition, fan runs but no heat	Check sail switch and limit switch
Atwood AFMD30111	Burner ignites but shuts down after seconds	Verify gas pressure and airflow
Dometic DFMD20121	No power to ignition	Check fuse, battery, and wiring

How To Reset An RV Furnace

Some RV furnaces can be reset to clear minor errors or restore operation. To do this:

1. Turn off the furnace using the thermostat or on/off switch.
2. Wait 30 seconds to allow the circuit board to reset.
3. Turn the furnace back on and set the desired temperature.

If this does not resolve the issue, deeper troubleshooting or professional service is recommended.

How To Stay Warm If Repairs Are Delayed

If your RV furnace remains inoperable, temporary heating solutions can help maintain comfort:

• Use electric portable heaters (with adequate ventilation).
• Layer thermal curtains or window covers to retain heat.
• Bundle up with extra blankets and sleeping bags.
• Insulate the RV floor and seal any drafts.

Frequently Asked Questions About RV Furnace Blowing Cold Air

Can I Fix An RV Furnace Myself?

Many basic issues—thermostat settings, breakers, propane levels—are DIY-friendly. Complex repairs (igniter, circuit board, or gas valves) should be left to professionals for safety reasons.

Why Does My Furnace Fan Run But No Heat Comes Out?

This usually means the ignition system failed, fuel is blocked, or air switches are faulty. The fan runs as part of the ignition cycle, but with no flame, only cold air circulates.

What If My Furnace Works Sometimes But Not Always?

Intermittent issues suggest loose wiring, sensor issues, or low battery voltage. Document symptoms and patterns to help diagnose the root cause.

Are RV Furnaces Safe To Repair?

Basic troubleshooting is usually safe, but working on gas systems or electrical circuits carries risks. Always turn off power/propane before attempting repairs. If unsure, consult a professional.

Parts And Tools For Basic RV Furnace Repairs

Stocking up on essential tools can make in-camp repairs easier and faster:

• Multimeter for voltage and continuity tests
• Extra fuses and thermostat batteries
• Adjustable wrenches and screwdrivers
• Soft cleaning brushes or canned air
• Manufacturer manuals for error codes

How To Find RV Furnace Replacement Parts

Replacement parts are available from most RV supply stores and online retailers. Always use model-specific components and verify part compatibility before buying. It’s advisable to keep key spares onboard.

How Long Should An RV Furnace Last?

With regular maintenance, most RV furnaces last 10–20 years. Neglected units often fail earlier due to moisture, corrosion, or soot buildup.

Tips For Optimizing RV Furnace Performance

• Keep intake and exhaust vents clear of snow, dirt, and nests.
• Operate the furnace regularly to reduce startup issues.
• Install a low-voltage cutoff to prevent furnace operation on a weak battery.
• Use high-quality propane to prevent burner contamination.

Understanding RV Furnace Error Codes

Many modern RV furnaces feature diagnostic lights or flashing codes to pinpoint problems. Check your furnace manual for a code guide, or consult the manufacturer’s website for troubleshooting steps aligned with each code.

Key Points To Remember

• Blowing cold air usually indicates an ignition, propane, power, or airflow issue.
• Most furnaces require both propane and 12V power to work properly.
• Routine maintenance mitigates most furnace problems before they start.
• Safety and manufacturer guidelines should always be followed during repairs.

Helpful Resources For RV Owners

For further research and support, explore RV owner forums, manufacturer websites, and maintenance videos on YouTube. These can provide model-specific tips and real-world troubleshooting advice.