Armstrong Error Code Search

Error code search offers information on the cause of the malfunction and the status of your air conditioner by entering the error code.


  1. This page provides a simple explanation concerning content relating to error codes and their possible causes. Please note that the content may slightly differ depending on the model.

2. It is always advised that you consult with an HVAC repair professional before attempting to provide any repairs yourself.

3. Precision Air assumes no responsibility for any accidents or troubles caused in the disassembly or repair of equipment performed according to the information on this page.

Armstrong Air Conditioner


If molded case circuit breakers or earth leakage circuit breakers have tripped, do not reset the breaker immediately without first checking for any problems with the insulation of equipment.

Resetting breakers without a check of insulation may cause damage to equipment.

Armstrong Air Conditioning Codes:


CODE: E105
RESULT: Device communication problem – No other devices on RS BUS (Communicating systems only).

CODE: E110
RESULT: Low line voltage.

CODE: E111
RESULT: Line voltage polarity reversed.

CODE: E112
RESULT: Ground not detected.

CODE: E113
RESULT: High line voltage.

CODE: E114
RESULT: Line voltage frequency out of range.

CODE: E115
RESULT: Low 24V.

CODE: E116
RESULT: High 24V.

CODE: E117
RESULT: Poor ground detected (Warning only).

CODE: E120
RESULT: Unresponsive device (Communicating systems only).

CODE: E124
RESULT: Active communicating thermostat signal missing for more than 3 minutes (Communicating systems only).

CODE: E125
RESULT: Control failed self check, internal error, failed hardware. Will restart if error recovers, Integrated control not communicating Covers hardware errors (flame sense circuit faults, pin shorts, etc).

CODE: E126
RESULT: Control internal communication problem.

CODE: E131
RESULT: Corrupted control parameters (Verify configuration of system) (Communicating systems only).

CODE: E180
RESULT: Outdoor air temperature sensor failure. Only shown if shorted or out of range (Communicating systems only).

CODE: E200
RESULT: Hard Lock out – Rollout circuit open or previously open.

CODE: E201
RESULT: Indoor blower/communication failure. Unable to communicate with blower motor.

CODE: E202
RESULT: Indoor blower motor mismatch – indoor motor horsepower does not match unit capacity.

CODE: E203
RESULT: Appliance capacity size is NOT programmed. Invalid unit codes. Refer to the configuration flow chart.

CODE: E204
RESULT: Gas valve miswired.

CODE: E205
RESULT: Gas valve control relay contact shorted.

CODE: E206
RESULT: Gas valve second stage relay failure.

CODE: E207
RESULT: Hot surface igniter sensed open 

CODE: E223
RESULT: Low pressure switch failed open.

CODE: E224
RESULT: Low pressure switch failed closed. Refer to troubleshooting.

CODE: E225
RESULT: High pressure switch failed open. Refer to troubleshooting.

CODE: E226
RESULT: High pressure switch failed closed. Refer to troubleshooting.

Air Conditioning services

Book a repair online

Book a repair in 2 minutes through our simple online process.