RV Furnace Blowing Cold Air? Fix Ignition Issues Fast

Tools & Parts Needed

Find these on Amazon: Fine Steel Wool Pads , Compressed Air Canister , Digital Multimeter

The Problem

When your RV furnace fan runs but only blows cold air with failed ignition attempts, you're dealing with an ignition system failure. The most common causes are a dirty flame sensor, blocked combustion air intake, faulty ignition control board, or propane supply issues.

What's Going Wrong

Start with cleaning the flame sensor and checking air intakes before moving to electrical components.

Dirty Flame Sensor: The flame sensor detects when the burner is lit. Even a thin layer of oxidation can prevent proper flame detection, causing the system to shut down for safety.

Blocked Air Supply: RV furnaces need adequate combustion air. External vents can become blocked by debris, especially after storage or camping in dusty conditions.

Failed Ignition Control Module: The electronic control board manages the ignition sequence. These can fail due to voltage fluctuations, moisture, or age, particularly in Suburban NT and Dometic furnaces.

Propane Supply Issues: Low tank pressure, air in the lines, or regulator problems can prevent proper gas flow to the burner assembly.

The Solution

You'll need:

• Screwdriver set (Phillips and flathead)
• Fine steel wool or sandpaper (400-grit)
• Compressed air canister
• Digital multimeter
• Flashlight or headlamp
• Shop vacuum
• Wire brush

Follow these steps:

1. Safety First: Turn off the furnace and shut off the propane supply at the tank. Allow 10 minutes for any gas to dissipate before beginning work.
2. Access the Furnace: Remove the furnace access panel, typically located inside a cabinet or behind a wall vent. Most panels are held by 4-6 screws.
3. Inspect the Flame Sensor: Locate the flame sensor (a small metal rod near the burner). Remove it by unscrewing the mounting screw. Clean the sensor thoroughly with fine steel wool or 400-grit sandpaper until it's shiny. A dirty sensor is the #1 cause of ignition failures.
4. Check Combustion Air Intake: Inspect the outside air intake vent for blockages like leaves, debris, or insect nests. Clean thoroughly with compressed air and a wire brush.
5. Examine the Burner Assembly: Look for spider webs, dust, or debris around the burner ports. Use compressed air to blow out any obstructions.
6. Test the Ignition Board: Ensure power is disconnected before handling. Touch a grounded metal surface to discharge static electricity. Look for the control board (usually a rectangular module with wires). Check for loose connections, corrosion, or burn marks. If the board shows physical damage, replacement is needed.
7. Verify Gas Pressure: Ensure your propane tank has adequate pressure. Test other propane appliances (stove, water heater) to confirm gas supply.
8. Check the Limit Switch: Locate the high-temperature limit switch (usually near the heat exchanger). If it's tripped, identify and address the cause of overheating before resetting, or replace if faulty.
9. Reassemble and Test: Reinstall all components, turn on propane, and test the furnace. Listen for proper ignition sequence: fan starts, then igniter clicks, followed by the whoosh of gas igniting.

Situations That Need a Professional

Call a certified RV technician if: You smell strong propane odors during operation, the ignition control board shows burn damage, you're uncomfortable working with propane systems, or multiple troubleshooting attempts have failed. Gas appliance repairs can be dangerous and may require specialized tools and certification.

Additionally, if your RV is still under warranty, professional repair may be required to maintain coverage.

Preventive Measures

Regular Maintenance: Clean the flame sensor at the start of each camping season. Inspect and clean exterior vents monthly during use.

Proper Storage: Cover exterior vents during storage to prevent insect intrusion. Run the furnace briefly each month during storage to prevent component stagnation.

Monitor Performance: Pay attention to ignition timing and flame color. Yellow or irregular flames indicate combustion problems that should be addressed promptly.

Annual Service: Have your furnace professionally serviced annually, including gas pressure testing and complete system inspection.