Dometic / Atwood 37021 Furnace Limit Switch – 8900-II / 8900-III Series

Dometic / Atwood 37021 Furnace Limit Switch – 8900-II / 8900-III Series

Genuine OEM Replacement

Part Number: 37021
Product Type: Furnace Limit Switch (High Temperature Safety Switch)
Application: Atwood HydroFlame® 8900-II & 8900-III Series Furnaces

Product Overview

The Dometic / Atwood 37021 Furnace Limit Switch is a genuine OEM high-temperature safety switch designed for select Atwood HydroFlame® 8900-II and 8900-III series furnaces.

This limit switch monitors the internal temperature of the furnace and automatically interrupts burner operation if temperatures exceed safe operating limits. It plays a critical role in preventing overheating and protecting the heat exchanger and surrounding components.

If your furnace is shutting down after ignition, short-cycling once warmed up, or failing to maintain burner operation, a weak or failed limit switch may be the cause. Replacing it with OEM Part 37021 restores safe, reliable heating performance.

Manufactured to original equipment specifications, this component ensures proper fitment and dependable operation.

Key Features

• Genuine OEM Dometic / Atwood replacement part
• High-temperature overheat protection
• Designed for 8900-II and 8900-III furnaces
• Restores safe furnace operation
• Direct replacement for original factory-installed switch
• Manufactured to original equipment standards

Compatible Furnace Models

Atwood HydroFlame® 8900-II Series

• 8935-AC-II
• 8935-DC-II
• 8940-AC-II
• 8940-DC-II

Atwood HydroFlame® 8900-III Series

• 8935-AC-III
• 8935-DC-III
• 8940-AC-III
• 8940-DC-III

Always verify your exact furnace model on the unit data plate before ordering.

When Should You Replace the Limit Switch?

You may need to replace the limit switch if you notice:

• Furnace ignites but shuts off quickly
• Repeated short cycling
• Burner operation stops once furnace heats up
• Diagnostic testing confirms limit switch failure

The limit switch is a critical safety device and should always be replaced with the correct OEM part.

Product Specifications

• Manufacturer: Dometic / Atwood
• Part Number: 37021
• Component: High Limit Safety Switch
• Application: 8900-II & 8900-III Series
• Includes: Limit switch only

Frequently Asked Questions (FAQ)

Q: What does a furnace limit switch do?

A: It prevents overheating by shutting off the burner circuit when internal temperatures exceed safe limits.

Q: Will this fit 8900-I furnaces?

A: This listing is specifically for 8900-II and 8900-III series models. Always confirm your furnace series before ordering.

Q: Is this an OEM Dometic / Atwood part?

A: Yes. Part 37021 is a genuine OEM replacement component.

Q: Can a bad limit switch cause short cycling?

A: Yes. A weak or failing limit switch can cause the furnace to shut down prematurely after ignition.