Suburban 521166 Water Heater Control Board – SAW6D, SAW6DE & SAW6DEL

The Suburban 521166 Water Heater Control Board is the OEM 12V Direct Spark Ignition (DSI) module board used specifically on Suburban SAW6-Series RV water heaters.

This board controls the propane ignition sequence, including spark generation, gas-valve operation, and flame sensing. It is not the same board used on the standard SW-Series water heaters. Suburban identifies 521166 specifically for the SAW6D, SAW6DE, and SAW6DEL Atwood-replacement water heater models.

Models It Fits

The Suburban 521166 fits:

• SAW6D

• SAW6DE

• SAW6DEL

These are Suburban’s SAW6 Atwood-replacement water heaters, designed as direct-fit replacement units for certain legacy Atwood installations.

Important Fitment Note

The 521166 is NOT the standard control board for SW6D, SW6DE, or SW6DEL water heaters.

The model prefix matters:

• SAW6D / SAW6DE / SAW6DEL → 521166

• Standard SW-Series DSI models → typically use 520814, depending on model and production range

Suburban’s own warranty documentation specifically separates the two as SW/SAW module board kits 520814 and 521166, confirming that 521166 is the SAW-specific board.

What the 521166 Control Board Does

The 521166 manages the Direct Spark Ignition sequence on the SAW6 water heater.

When the thermostat calls for heat, the board:

• Initiates the ignition sequence

• Sends high-voltage spark to the ignition electrode

• Energizes the LP gas valve

• Monitors burner flame through the flame-sensing circuit

• Maintains operation while a valid flame is present

• Shuts down or enters ignition lockout if flame is not established

The board acts as the central electronic controller for the propane burner system.

Signs & Symptoms of a Failed Control Board

A faulty 521166 may cause:

• SAW6 water heater will not ignite

• No spark at the burner

• Gas valve does not energize

• Burner lights but immediately shuts back off

• Water heater repeatedly attempts ignition and locks out

• Intermittent propane operation

• Other ignition components test correctly but the heater still will not operate

Before replacing the board, verify the 12V DC power supply, ground, thermostat/high-limit circuit, ignition electrode, gas valve, propane supply, and wiring connections.

SAW6 vs. SW6

The SAW6 family should not be confused with the much more common SW6 family.

Suburban developed the SAW models as Atwood replacement water heaters, and they use some components that differ from conventional SW-Series heaters.

For this reason, a customer with an SW6D should not order 521166 simply because the model number contains “6D.” The data plate must specifically identify the heater as an SAW6D, SAW6DE, or SAW6DEL.

Estimated Install Time

Approximately 15–30 minutes for most installations.

Tools Required

• Phillips screwdriver

• Nut driver or basic hand tools

• Multimeter

• Electrical contact cleaner if needed

Installation Notes

Disconnect 12V DC power and shut off the LP gas supply before servicing the water heater.

Before removing the existing board:

1. Photograph the wiring and connector locations.

2. Verify the water heater data plate says SAW6D, SAW6DE, or SAW6DEL.

3. Inspect connectors for corrosion, overheating, or loose terminals.

4. Confirm that the board is receiving proper 12V power and ground.

A poor ground or low supply voltage can mimic the symptoms of a failed ignition board.

Potential Issues

A no-ignition condition does not automatically mean the control board has failed. Similar symptoms can be caused by:

• Low 12V battery voltage

• Poor ground connection

• Faulty ignition electrode

• Incorrect electrode gap

• Failed thermostat or high-limit switch

• Faulty gas valve

• Low LP gas pressure

• Loose or corroded connectors

Proper diagnosis before replacement can help avoid replacing a functioning control board.

Product Specifications

Manufacturer: Suburban / Airxcel
Part Number: 521166
Part Type: DSI Ignition Control / Module Board
Operating Voltage: 12V DC
Fits: SAW6D, SAW6DE, SAW6DEL
Application: Suburban SAW6 Atwood-Replacement RV Water Heaters
Includes: Control board only

Warranty

Suburban’s current warranty documentation identifies the 521166 SAW water-heater module board kit as carrying a 3-year replacement-part warranty with no labor allowance.

Important

The Suburban 521166 fits SAW6-Series water heaters only. Do not order this board for a standard SW6D, SW6DE, or SW6DEL unless the original water-heater data plate specifically identifies the unit as an SAW6 model.