M.C. Enterprises 31093MC Furnace Low Air Flow Switch (Sail Switch)

For Atwood Hydroflame AF Small Series Furnaces – Serial Numbers BEFORE 72498929
Aftermarket Replacement

Part Number: 31093MC
Manufacturer: M.C. Enterprises
Product Type: Furnace Low Air Flow Switch (Sail Switch)
Application: Atwood HydroFlame AF Small Series Furnaces

Product Overview

The M.C. Enterprises 31093MC Furnace Low Air Flow Switch is an aftermarket sail switch designed specifically for Atwood HydroFlame AF small series furnaces manufactured BEFORE serial number 72498929.

Also known as a sail switch, this component verifies proper blower airflow before allowing the furnace ignition sequence to begin. If sufficient airflow is not detected, the burner will not ignite — protecting the furnace from unsafe combustion.

If your RV furnace blower runs but no flame appears, ignition is intermittent, or the unit shuts down shortly after startup, a faulty sail switch is one of the most common causes.

The 31093MC provides a reliable and cost-effective replacement for early-production AF small-series furnaces.

⚠ Important Compatibility Notice

This sail switch is ONLY compatible with furnaces manufactured BEFORE Serial Number 72498929.

Always verify both your furnace model number and serial number before ordering.

Compatible Furnace Models

Dometic / Atwood Furnaces with Serial Numbers BEFORE 72498929

AFMD Series

AFMD16111
AFMD16121
AFMD16131
AFMD16141
AFMD16151

AFMD20111
AFMD20121
AFMD20131
AFMD20141
AFMD20151

AFSAD Series

AFSAD12111
AFSAD12121
AFSAD12131
AFSAD12141

AFSD Series

AFSD12111
AFSD12121
AFSD12131
AFSD12141

AFSD16111
AFSD16121
AFSD16131
AFSD16141

AFSD20121
AFSD20131
AFSD20141

If your furnace serial number is AFTER 72498929, a different sail switch is required.

Key Features

• Aftermarket replacement for early Atwood small series furnaces
• Designed for units manufactured before serial 72498929
• Verifies airflow before ignition
• Helps resolve “blower runs but no heat” issues
• Restores proper ignition sequencing
• Direct-fit design for compatible models

Common Symptoms of a Failed Sail Switch

You may need to replace the sail switch if:

• Blower motor runs but burner will not ignite
• Furnace attempts ignition then shuts down
• Heating works intermittently
• Airflow-related ignition faults occur
• Paddle arm is bent, sticking, or obstructed

The sail switch is one of the most frequently replaced RV furnace parts in small AF series units.

Product Specifications

Manufacturer: M.C. Enterprises
Part Number: 31093MC
Component: Low Air Flow Switch (Sail Switch)
Application: AF Small Series (Pre-Serial 72498929)
Type: Aftermarket Replacement

Frequently Asked Questions (FAQ)

Q: Why does the serial number matter?
A: Furnace airflow switch designs changed after serial number 72498929, requiring a different sail switch.

Q: Will this fit AFSD furnaces made after that serial number?
A: No. Later models require a different part number.

Q: What does a sail switch do?
A: It verifies adequate airflow before allowing ignition.

Q: Is this an OEM Dometic part?
A: No. This is an aftermarket replacement manufactured by M.C. Enterprises.