Armstrong Air
Armstrong Air Air Conditioners Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E0
The outdoor unit will not run, even though the thermostat is calling for cooling. The indoor blower may run, but the condenser is completely off.
Communication Fault Between Indoor and Outdoor Control Boards
E1
The outdoor unit runs briefly, then shuts down. The status LED on the control board flashes E1, and cooling is intermittent.
High Pressure Switch Open
E2
The outdoor unit will not start, and the control board shows E2. The compressor and fan remain off, even though the thermostat is calling.
Low Pressure Switch Open
E3
The outdoor unit attempts to start, then shuts down with an E3 indication. The compressor is hot to the touch.
Compressor Overload / High Discharge Temperature
E4
The outdoor unit runs, but the indoor temperature does not drop. The control board shows E4, and the suction line may be very cold or frosted.
Evaporator Coil Temperature Sensor Fault / Freeze Protection Trip
E5
The outdoor unit does not start, and the control board indicates E5. The indoor blower may run normally.
Outdoor Ambient Temperature Sensor Fault
E6
The outdoor unit starts and stops repeatedly, an E6 code is logged, and the compressor may not start reliably.
Compressor Start Failure / Locked Rotor Protection
E7
Outdoor unit runs but the indoor blower does not, or the blower runs at an incorrect speed. E7 is logged on communicating systems.
Indoor Blower Motor Communication / ECM Fault
E8
The system shuts down during operation with E8 indicated, which may coincide with very low indoor airflow and coil icing.
Indoor Coil Airflow Fault / Blower Overcurrent
E9
The system will not run in cooling mode, an E9 code is present on the communicating thermostat or board, and other functions may be locked out.
Configuration / Setup Error in Communicating System
F1
The indoor unit control board flashes F1, and the blower may not start or runs erratically in cooling mode.
Indoor Control Board Fault / EEPROM Error
F2
The indoor unit flashes F2, cooling may be locked out, and the thermostat may show an indoor temperature error.
Indoor Temperature Sensor / Thermistor Fault
F3
The indoor unit flashes F3, the blower may shut down during cooling, and the coil may be very cold.
Evaporator Coil Sensor Fault / Freeze Protection
F4
Indoor unit flashes F4, blower may run but cooling is disabled, and the thermostat may show a system fault.
High Temperature Limit / Supply Air Overheat in Cooling Mode
F5
Indoor unit flashes F5, the system may short-cycle or lock out, and the thermostat may show a communication error.
Thermostat Communication Fault (Communicating Systems)
H0
The outdoor unit does not enter defrost mode in heat pump operation (for Armstrong Air heat pump models), and an H0 code or similar is displayed.
Defrost Control Fault
H1
The heat pump frequently enters defrost mode or stays in defrost too long, and an H1 or similar code is logged.
Defrost Sensor Out of Calibration / Shorted
L1
The outdoor unit is completely dead, an L1 or line-voltage fault is indicated on the control board, and there is no LED activity.
Line Voltage Loss or Phase Fault (for 3-phase commercial Armstrong Air units)
L2
The outdoor unit intermittently shuts down, an L2 or low-voltage fault is indicated, and the thermostat may go blank.
Low Voltage (24 VAC) Supply Fault
Symptom
Burning or electrical smell from indoor or outdoor unit during cooling
Overheating Electrical Component
Symptom
Indoor blower runs, but the outdoor fan does not; the compressor may or may not run, and the unit hums.
Condenser Fan Motor Failure
Symptom
Indoor coil repeatedly freezes into a block of ice during cooling
Evaporator Coil Freeze-Up
Symptom
Indoor temperature varies widely between rooms during cooling
Uneven Cooling / Air Distribution Problem
Symptom
Indoor unit produces a musty or moldy odor when cooling starts
Biological Growth on Evaporator Coil or Drain Pan
Symptom
Indoor unit runs, but water leaks from around the air handler or furnace during cooling.
Condensate Drain Backup / Pan Overflow
Symptom
Loud buzzing or chattering noise from outdoor unit contactor area
Contactor Chatter / Coil Voltage Instability
Symptom
Outdoor unit hums loudly, but the compressor does not start, then shuts off due to overload.
Compressor Hard Start / Locked Rotor
Symptom
Outdoor unit makes loud grinding or squealing noises during operation
Mechanical Noise from Condenser Fan or Compressor
Symptom
Outdoor unit runs continuously and does not shut off even when thermostat is satisfied
Stuck Contactor or Control Signal
Symptom
Outdoor unit runs, but air from indoor vents is warm or only slightly cool.
Loss of Cooling Capacity
Symptom
Outdoor unit vibrates excessively and is very noisy during operation
Excessive Vibration / Mounting Issues
Symptom
Outdoor unit will not start at all; the indoor blower runs, and the thermostat appears normal.
Outdoor Unit No-Start
Symptom
System frequently trips the main breaker when starting or during operation
Overcurrent / Electrical Overload
Symptom
System will not start after a power outage, even though power has been restored
Post-Outage Lockout / Brownout Protection
Symptom
The indoor blower does not run in cooling, but the outdoor unit runs normally.
Indoor Blower Motor Not Operating
Symptom
The system short-cycles, turning on and off frequently without reaching the set temperature.
Short Cycling
Symptom
Thermostat display is blank and system does not respond
Thermostat Power Loss
Symptom
Water dripping from supply registers or sweating on ductwork during cooling.
Ductwork Condensation
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E0 |
The outdoor unit will not run, even though the thermostat is calling for cooling. The indoor blower may run, but the condenser is completely off.
|
Communication Fault Between Indoor and Outdoor Control Boards | View Details |
| E1 |
The outdoor unit runs briefly, then shuts down. The status LED on the control board flashes E1, and cooling is intermittent.
|
High Pressure Switch Open | View Details |
| E2 |
The outdoor unit will not start, and the control board shows E2. The compressor and fan remain off, even though the thermostat is calling.
|
Low Pressure Switch Open | View Details |
| E3 |
The outdoor unit attempts to start, then shuts down with an E3 indication. The compressor is hot to the touch.
|
Compressor Overload / High Discharge Temperature | View Details |
| E4 |
The outdoor unit runs, but the indoor temperature does not drop. The control board shows E4, and the suction line may be very cold or frosted.
|
Evaporator Coil Temperature Sensor Fault / Freeze Protection Trip | View Details |
| E5 |
The outdoor unit does not start, and the control board indicates E5. The indoor blower may run normally.
|
Outdoor Ambient Temperature Sensor Fault | View Details |
| E6 |
The outdoor unit starts and stops repeatedly, an E6 code is logged, and the compressor may not start reliably.
|
Compressor Start Failure / Locked Rotor Protection | View Details |
| E7 |
Outdoor unit runs but the indoor blower does not, or the blower runs at an incorrect speed. E7 is logged on communicating systems.
|
Indoor Blower Motor Communication / ECM Fault | View Details |
| E8 |
The system shuts down during operation with E8 indicated, which may coincide with very low indoor airflow and coil icing.
|
Indoor Coil Airflow Fault / Blower Overcurrent | View Details |
| E9 |
The system will not run in cooling mode, an E9 code is present on the communicating thermostat or board, and other functions may be locked out.
|
Configuration / Setup Error in Communicating System | View Details |
| F1 |
The indoor unit control board flashes F1, and the blower may not start or runs erratically in cooling mode.
|
Indoor Control Board Fault / EEPROM Error | View Details |
| F2 |
The indoor unit flashes F2, cooling may be locked out, and the thermostat may show an indoor temperature error.
|
Indoor Temperature Sensor / Thermistor Fault | View Details |
| F3 |
The indoor unit flashes F3, the blower may shut down during cooling, and the coil may be very cold.
|
Evaporator Coil Sensor Fault / Freeze Protection | View Details |
| F4 |
Indoor unit flashes F4, blower may run but cooling is disabled, and the thermostat may show a system fault.
|
High Temperature Limit / Supply Air Overheat in Cooling Mode | View Details |
| F5 |
Indoor unit flashes F5, the system may short-cycle or lock out, and the thermostat may show a communication error.
|
Thermostat Communication Fault (Communicating Systems) | View Details |
| H0 |
The outdoor unit does not enter defrost mode in heat pump operation (for Armstrong Air heat pump models), and an H0 code or similar is displayed.
|
Defrost Control Fault | View Details |
| H1 |
The heat pump frequently enters defrost mode or stays in defrost too long, and an H1 or similar code is logged.
|
Defrost Sensor Out of Calibration / Shorted | View Details |
| L1 |
The outdoor unit is completely dead, an L1 or line-voltage fault is indicated on the control board, and there is no LED activity.
|
Line Voltage Loss or Phase Fault (for 3-phase commercial Armstrong Air units) | View Details |
| L2 |
The outdoor unit intermittently shuts down, an L2 or low-voltage fault is indicated, and the thermostat may go blank.
|
Low Voltage (24 VAC) Supply Fault | View Details |
| – |
Burning or electrical smell from indoor or outdoor unit during cooling
|
Overheating Electrical Component | View Details |
| – |
Indoor blower runs, but the outdoor fan does not; the compressor may or may not run, and the unit hums.
|
Condenser Fan Motor Failure | View Details |
| – |
Indoor coil repeatedly freezes into a block of ice during cooling
|
Evaporator Coil Freeze-Up | View Details |
| – |
Indoor temperature varies widely between rooms during cooling
|
Uneven Cooling / Air Distribution Problem | View Details |
| – |
Indoor unit produces a musty or moldy odor when cooling starts
|
Biological Growth on Evaporator Coil or Drain Pan | View Details |
| – |
Indoor unit runs, but water leaks from around the air handler or furnace during cooling.
|
Condensate Drain Backup / Pan Overflow | View Details |
| – |
Loud buzzing or chattering noise from outdoor unit contactor area
|
Contactor Chatter / Coil Voltage Instability | View Details |
| – |
Outdoor unit hums loudly, but the compressor does not start, then shuts off due to overload.
|
Compressor Hard Start / Locked Rotor | View Details |
| – |
Outdoor unit makes loud grinding or squealing noises during operation
|
Mechanical Noise from Condenser Fan or Compressor | View Details |
| – |
Outdoor unit runs continuously and does not shut off even when thermostat is satisfied
|
Stuck Contactor or Control Signal | View Details |
| – |
Outdoor unit runs, but air from indoor vents is warm or only slightly cool.
|
Loss of Cooling Capacity | View Details |
| – |
Outdoor unit vibrates excessively and is very noisy during operation
|
Excessive Vibration / Mounting Issues | View Details |
| – |
Outdoor unit will not start at all; the indoor blower runs, and the thermostat appears normal.
|
Outdoor Unit No-Start | View Details |
| – |
System frequently trips the main breaker when starting or during operation
|
Overcurrent / Electrical Overload | View Details |
| – |
System will not start after a power outage, even though power has been restored
|
Post-Outage Lockout / Brownout Protection | View Details |
| – |
The indoor blower does not run in cooling, but the outdoor unit runs normally.
|
Indoor Blower Motor Not Operating | View Details |
| – |
The system short-cycles, turning on and off frequently without reaching the set temperature.
|
Short Cycling | View Details |
| – |
Thermostat display is blank and system does not respond
|
Thermostat Power Loss | View Details |
| – |
Water dripping from supply registers or sweating on ductwork during cooling.
|
Ductwork Condensation | View Details |
No matching codes found
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