Goodman furnace 11 red flashes: Limit switch open due to blower failure
Eleven red flashes means the limit switch opened and the control has attributed it to the blower rather than to airflow restriction. The furnace overheated because the blower did not move air.
Applies to: Goodman GMEC96 and Amana AMEC96 two-stage gas furnaces with a three-colour diagnostic LED.
What it means
This code is more specific than a plain open limit switch, and the extra specificity is useful. The control has seen the limit open and has determined the blower is the reason — it was commanded to run and either did not, or did not deliver. That distinguishes it from the four red flash code, where the limit opened for reasons that could include a dirty filter, closed registers, or ductwork. Here the control is pointing at the blower itself, which narrows the investigation to the motor, its power, and its control circuit.
Most common causes
- A failed blower motor.
- A failed blower capacitor, on motors that use one.
- A blower motor not receiving power from the control board.
- A failed blower relay on the control board.
- A seized blower wheel or an obstruction preventing rotation.
- A wiring fault in the blower circuit.
- A blower door switch not made, cutting power to the blower circuit.
How to diagnose it
- Note whether the blower runs at all — on a fan-only thermostat setting, or during cooling. A blower that runs in one mode and not another points at the control circuit rather than the motor.
- Check the blower door is properly seated, since the door switch cuts power and a door not closed produces confusing symptoms.
- Listen at the start of a heating cycle for the blower attempting to start.
- Note whether the furnace fires and then shuts down shortly afterwards, which is the sequence this code describes.
How to fix it
- Refit the blower door properly if it was not seated.
- Everything else is technician work — the blower motor, capacitor, relay, and wiring all sit in the high voltage side of the furnace.
- Do not run the furnace in heat with a blower that is not working. The limit will stop it, but repeatedly overheating the heat exchanger is what cracks it.
- Have the cause of any obstruction established rather than just cleared, since something that got into the blower once can get in again.
Notes
A furnace that fires briefly and then shuts down, repeatedly, with no heat reaching the house is the usual presentation. The heat exchanger is being heated with no air moving over it each time, which is precisely the condition the limit switch exists to stop.