Rv Furnace Sail Switch Location and Troubleshooting Guide

The sail switch is a small but critical safety device in an RV furnace that confirms airflow from the blower before allowing ignition. This guide explains common RV furnace sail switch locations, how it works, symptoms of failure, testing procedures, replacement tips, and preventive maintenance to keep an RV heating system reliable and safe.

Furnace Brand/Model	Typical Sail Switch Location	Access Tip
Suburban	On the blower housing near the main air intake duct	Remove exterior service door; inspect left side of blower
Dometic/Waeco	Mounted on blower tube or plenum downstream of blower	Access through interior furnace cover or bottom service panel
Atwood	On intake duct between blower and heat exchanger	Open furnace front panel; follow small vacuum hose

What Is A Sail Switch And Why Location Matters

The sail switch is a pressure- or airflow-actuated switch with a small paddle or “sail” that moves when the furnace blower runs. It prevents ignition unless adequate airflow is present to remove combustion gases and heat. Location matters because the switch must sense reliable airflow representative of the heat exchanger’s cooling path. Incorrect placement can cause nuisance lockouts or unsafe operation.

Common RV Furnace Sail Switch Locations

Manufacturers place sail switches in a few predictable spots. Knowing these typical locations speeds diagnosis and repair when a furnace refuses to light or runs intermittently.

On The Blower Housing

Many RV furnace designs mount the sail switch directly on the blower housing or motor bracket. The paddle sits in the blower’s airstream so movement directly corresponds to motor output.

In The Intake Or Plenum Duct

Some installations put the sail switch in the intake duct or plenum between the blower and heat exchanger. This position checks air movement through the entire heat path rather than only at the motor outlet.

Near The Heat Exchanger Outlet

Less commonly, the switch sits near the heat exchanger outlet or flue area. This placement ensures airflow where the exchanger must be cooled, but access can be harder.

Connected By A Small Tube Or Remote Paddle

Some systems use a remote paddle or vacuum tube to locate the sensing element where space constraints prevent direct mounting. Follow wiring and tubing to find the remote switch.

How To Identify The Sail Switch In An RV Furnace

Identification involves visual cues and following simple wiring. The sail switch usually has a small rectangular or circular body with two electrical terminals and a movable plastic or metal paddle.

• Look For A Small Paddle Or Flapper In The Air Stream.
• Trace Two Wires From The Furnace Control Board To A Small Switch.
• Follow A Thin Vacuum Or Tubing That Leads To A Remote Sensor.

Safety Tip: Always disconnect power and propane before removing covers or testing components.

Symptoms Of A Faulty Or Mislocated Sail Switch

A malfunctioning or poorly located sail switch causes heating problems and may trigger safety lockouts. Common symptoms include:

• Furnace Starts Blower But Then Shuts Off Without Igniting.
• Continuous Blower Operation With No Ignition Attempts.
• Intermittent Ignition Failures Or Cycling.
• Visible Damage Or Sticking Of The Paddle.

These symptoms often prompt error codes or LED flashes on modern furnaces; consult the furnace manual for code interpretation.

Step-By-Step Diagnostics For Sail Switch Location Problems

The following diagnostic approach helps locate and confirm sail switch function and placement issues. Each step keeps the RV user safe and focuses on practical checks.

1. Visual Inspection

Turn off power and propane. Open the furnace service panel and inspect for a switch mounted near the blower or ducts. Look for a paddle and check for debris, broken mounts, or disconnected tubing.

2. Check For Proper Mounting Position

Ensure the paddle sits fully in the airstream and aligns with manufacturer markings. A bent or misaligned paddle reduces sensitivity. Confirm no gaps let bypass air avoid the sensor.

3. Test For Mechanical Movement

With power off, manually blow across the paddle or gently move it; it should snap open and closed. Stiction or weak springs indicate the need for cleaning or replacement.

4. Electrical Continuity Test

Use a multimeter set to continuity or ohms. With the blower off, the switch may be open; with the blower running (and safe to operate), the switch should close. If it fails to change state when airflow is present, replace the switch.

5. Simulate Correct Airflow

Where placement is suspect, simulate correct airflow with a shop vac or compressed air to confirm the furnace will ignite when the switch sees adequate flow. This helps verify whether the physical location senses representative airflow.

Replacement And Adjustment Tips

Replacing or adjusting a sail switch requires attention to position, wiring, and compatibility. The wrong switch or wrong placement can cause recurring issues.

Selecting The Correct Replacement

Match the replacement switch to the furnace brand and model. Key specs include pressure rating, paddle size, and electrical ratings. OEM parts are preferred when available.

Mounting And Orientation

Mount the new switch in the same orientation as the original. Ensure the paddle sits squarely in the airstream with no rubbing against the housing. Secure mounting prevents vibration-induced failures.

Wiring And Terminal Care

Reconnect terminals with proper insulated spade connectors. Avoid overstressing wires. If the switch uses a vacuum tube, ensure the tube is tight and routed to avoid kinks.

Common Installation Mistakes That Affect Sail Switch Performance

Incorrect installation often causes false lockouts or failed ignition. Key mistakes include:

• Mounting The Switch Too Far From The Airstream, Resulting In Weak Sensing.
• Routing Vacuum Tubing With Kinks Or Leaks That Reduce Pressure Signal.
• Using An Incorrectly Sized Paddle That Won’t Move At The Fan’s Air Volume.
• Poor Electrical Connections Causing Intermittent Open/Close Behavior.

Maintenance Practices To Keep The Sail Switch Reliable

Regular maintenance extends sail switch life and reduces downtime during cold weather. Recommended tasks are straightforward and effective.

• Inspect And Clean The Paddle Annually For Dust And Debris.
• Check Mounting And Fasteners For Looseness Or Vibration Damage.
• Verify Vacuum Tubing Integrity And Reroute If Necessary.
• Exercise The Switch Mechanically During Off-Season To Prevent Sticking.

Proactive Check: Include the sail switch in seasonal furnace checks before winter travel.

When To Call A Professional

Some situations warrant professional HVAC or RV technician help. Seek professional service if the switch is hard to access, if replacement requires disassembly of the heat exchanger, or if electrical issues beyond the switch are suspected.

Professional service is also recommended when the furnace shows persistent error codes after a switch replacement, indicating deeper control board, gas valve, or ignition problems.

Safety Considerations And Regulatory Notes

The sail switch is a safety device tied to combustion control. Any repairs involving gas, ignition, or major furnace disassembly should prioritize safety and compliance with appliance standards.

Safety Reminders: Disconnect propane and battery power before service. Use OEM parts and follow the furnace manual’s instructions to maintain compliance with appliance safety requirements.

Quick Reference: Locating The Sail Switch By Furnace Brand

Brand	Likely Location	Access Note
Suburban	Left or rear of blower housing	Exterior service door; inspect below furnace
Dometic	On blower tube or intake plenum	Interior panel removal may be required
Atwood	Between blower and heat exchanger	Front panel removal and visual trace of wires

Useful Tools And Parts For Sail Switch Work

Having the right tools speeds diagnostics and reduces errors. Useful items include:

• Multimeter For Continuity And Voltage Checks.
• Small Screwdrivers And Nut Drivers To Remove Panels.
• Replacement Sail Switch (OEM Where Possible).
• Spade Connectors, Electrical Tape, And Wire Tools.
• Compressed Air Or Soft Brush To Clean Paddle And Housing.

Final Practical Tips For RV Owners

Document the sail switch location and part number after service for faster future repairs. Keep a spare switch and basic tools on board during winter travel for quick field fixes. Regular preventive checks reduce the chance of being without heat in cold conditions.

When troubleshooting, follow a logical sequence: inspect, test mechanically, measure electrically, and then replace if necessary. This approach minimizes unnecessary parts replacement and ensures the long-term reliability of the RV furnace and safety systems.