Lennox S40 - Page 69

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Table 21. Lennox S40 Smart Thermostat Alert Codes and Troubleshooting
E2A=Errors to Action, GF= Gas Furnace, AH=Air Handler, IU=Indoor unit (GF or AH), HP=Heat Pump, AC=Air Conditioner, OU=Outdoor Unit (AC or HP), PA=Pure Air S, ZA=Zone system,
SRS=Smart Room Sensor, TS=Thermostat , IAQ- IAQ Monitor and WE=Wi-Fi Extender
Alert
Code
Inverter
Flash
Code
Priority
Condition
Actual Displayed Alert
Text Under dealer control
center > Notications
Component or System Operational State and Troubleshooting Tip
How to clear
alert code
417 Service Soon
OU Discharge Sensor
Faulty
System Detection and Operation:
The outdoor unit discharge line temperature sensor is either open, short-circuited or the temperature is out
of sensor range.
• This fault is detected by allowing the unit to run for 90 seconds before checking discharge line sensor
resistance.
• If the discharge sensor resistance is not within range after 90 second period, the control will display the
priority condition as service soon.
• If the service soon condition continues for 10 minutes, the system changes the priority condition to service
urgent.
Possible Causes:
• The applicable system component detects either an open, shorted or temperature out of range condition.
• Discharge sensor leads located in wrong pin positions in harness plug-in connector. Refer to the applicable
unit installation and service procedure and locate the terminal descriptions table to verify cable harness
assembly wiring pin positions are correct.
Possible Solutions:
• Check the resistance of the discharge sensor and compare to temperature resistance chart located in the
applicable unit installation and service procedure. If sensor resistance is out of range then replace the
discharge line temperature sensor.
• If discharge sensor wring leads are located in the wrong connector pin-out then order a replacement cable
assembly.
Automatically clears
after fault signal
condition is no longer
present.
418 Service Soon
OU EIM W Output
Hardware Fault
There is a faulty W output circuit.
• W terminal is energized while in cooling mode.
• Possible cause may be a stuck closed relay on the control, or something external to the control that is
energizing W terminal when it should not be energized.
• Disconnect any wiring from the W terminal.
• If 24VAC is still present on the terminal, then it is a stuck relay.
• If 24VAC disappears, then there is a need to check any of the wires hooked up to the W terminal.
Automatically clears
after fault signal is
removed.
419
Service
Urgent
OU EIM W Output
Hardware Fault
Lockout
The W output has reported more than ve errors.
• The system will shut down the outdoor unit.
• The W output (alert code 418) on the outdoor unit has reported more than ve strikes.
• Disconnect thermostat wire from W and verify there is no 24VAC on the W.
• If 24VAC is present, replace the outdoor control.
Automatically clears
after power recycled.
420 Service Soon
AH EIM Defrost Out Of
Cycle
The heat pump defrost cycle has taken more than 20 minutes to complete.
• Defrost cycle lasts longer than 20 minutes.
• Check heat pump operation.
• This is applicable only in communicating indoor unit with non-communicating heat pump.
Automatically clears
when W1 signal is
removed.