Bryant 355MAV Error Code 25: Model Selection or Setup Error
What Does Code 25 Mean?
Status code 25 on the Bryant 355MAV indicates that the model plug (PL4) is missing or incorrect, or that setup switches SW1-1 or SW1-6 are positioned improperly. The control board uses these switches and the model plug to identify the furnace configuration, and it cannot operate normally if the settings are wrong.
The most common scenario is that someone left SW1-1 or SW1-6 in the ON position after performing a diagnostic or setup procedure. Both switches should be in the OFF position during normal thermostat-controlled operation. SW1-1 is the setup/diagnostic switch, and SW1-6 is used for specific configuration functions. If both are ON simultaneously, the control also flags this error.
If the code only flashes 4 times on power-up and then stops, the control is defaulting to the model selection stored in its memory — this means it can still run, but the configuration may not be optimal. A missing or incorrect model plug (PL4) is less common and typically only occurs after a board replacement or if the plug was accidentally dislodged during maintenance.
Common Causes
How to Fix It: Check DIP Switch Positions
What You'll Need
- Flashlight
- Small flathead screwdriver (for DIP switch adjustment)
Steps
- Turn off power at the breaker or power switch and shut off the gas supply valve Locate your electrical panel and turn the furnace breaker to OFF. Find the gas shutoff valve on the gas line leading to the furnace and turn it to the closed (perpendicular to the pipe) position. If you smell gas, leave immediately and call your gas company.
- Access the control board Remove the blower access panel to expose the control board. The DIP switches are small toggle switches mounted directly on the board, typically labeled SW1.
- Check SW1-1 position Locate switch SW1-1 on the control board. For normal operation, SW1-1 must be in the OFF position. If it is in the ON position, use a small flathead screwdriver to gently slide it to OFF. This switch is used for setup and diagnostic modes and should never be left ON during regular operation.
- Check SW1-6 position Locate switch SW1-6. For normal operation, SW1-6 must also be in the OFF position. If it is ON, slide it to OFF. Having both SW1-1 and SW1-6 in the ON position simultaneously will also trigger this error.
- Restore power and gas Replace the access panel. Turn the gas supply valve back to open (parallel to the pipe). Turn the breaker back ON. The control board should reinitialize with the correct switch settings.
When to Call a Professional
Contact a licensed HVAC technician if:
- Both DIP switches are already in the correct OFF position but code 25 persists
- The model plug (PL4) appears to be missing or loose on the control board
- Code 25 appeared after a recent control board replacement
- The code flashes continuously rather than just 4 times on power-up
- You are unsure which DIP switch positions are correct for your specific installation