|Slow green flashing
||Coleman furnace is operating normally.
|Slow amber flashing
||Normal operation with a call for heat.
|Steady on red
||There's a control failure.
|Rapid red flashing
||There's a twinning error with incorrect 24V phasing.
||Check the twinning wiring.
|Rapid amber flashing
||There's a low flame sense current.
||Check and clean the flame sensor. If it's still an issue, check for proper gas flow.
|One red flash
||A flame's present with the gas turned off.
||Check the gas valve. It could be leaky or slow closing.
|Two red flashes
||Pressure switch is stuck in the closed position.
||Check if there is a faulty pressure switch or miswiring.
|Three red flashes
||Pressure switch is stuck in the open position.
||Check if there is a faulty inducer, a blocked vent pipe, a broken pressure switch hose, or a faulty pressure switch.
|Four red flashes
||Limit switch is stuck while open.
||Check for a a dirty filter, an improperly sized duct system, an incorrect blower speed setting, or a faulty blower motor.
|Five red flashes
||Rollout switch is stuck while open.
||The rollout control is manually reset. Therefore, if it has opened, then check to see if the inducer is operating properly or there is an issue with the primary heat exchanger.
|Six red flashes
||Pressure switch cycle has locked out.
||The furnace will lockout for one hour and then reset.
|Seven red flashes
||There's an ignition lockout due to too many retries.
||The flame couldn't be established, check for a faulty gas valve, a dirty or defective flame sensor, a faulty hot surface ignitor, or a problem with the burner.
|Eight red flashes
||There's an ignition lockout due to repeated power recycles.
||Check if there is low gas pressure, a dirty or defective flame sensor, or a faulty gas valve.
|Nine red flashes
||There's a grounding or line polarity issue.
||Check the polarity at both the furnace and branch.
|Ten red flashes
||Gas continues to flow with no call for heating.
||Check on the gas valve and the gas valve wiring.