HVAC Control Board Error Codes: Troubleshooting Guide

Reading Error Codes

Most modern furnaces use LED flash codes to indicate problems. Count the flashes and refer to the code chart on the furnace door.

Common Error Codes

• 1 flash: Normal operation
• 2 flashes: External lockout
• 3 flashes: Pressure switch error
• 4 flashes: Open high limit switch
• 5 flashes: Flame sensed without gas valve
• 6 flashes: Ignition failure
• 7 flashes: Rollout switch open

Resetting the Board

1. Turn off power for 30 seconds
2. Restore power and observe LED
3. If code persists, address the underlying issue