Lennox LIUH018021T431E-1 Service Manual page 139

2.4.4.6. F1, F2, F3 Malfunction
Error
E4 displayed
E4 displayed
Judge 1: Outdoor condenser temp. sensor (T3) is malfunctioning
Judge 1: Outdoor condenser temp. sensor (T3) is malfunctioning
Is the wiring of the condenser temp.
Is the wiring of the condenser temp.
sensor (T3) not connected properly?
sensor (T3) not connected properly?
Is the resistance of condenser temp.
Is the resistance of condenser temp.
sensor (T3) wrong according to
sensor (T3) wrong according to
Appendix 1?
Appendix 1?
Judge 2: Outdoor ambient temp. sensor (T4) is malfunctioning
Judge 2: Outdoor ambient temp. sensor (T4) is malfunctioning
Is the wiring of the outdoor ambient
Is the wiring of the outdoor ambient
temperature sensor (T4) not
temperature sensor (T4) not
connected properly
connected properly
Is the resistance of the outdoor
Is the resistance of the outdoor
ambient temperature sensor (T4)
ambient temperature sensor (T4)
wrong according to Appendix 1?
wrong according to Appendix 1?
Judge 3: Compressor discharge temp. sensor (T5) is malfunctioning
Judge 3: Compressor discharge temp. sensor (T5) is malfunctioning
Is the wiring of the compressor
Is the wiring of the compressor
discharge temperature sensor (T5)
discharge temperature sensor (T5)
disconnected?
disconnected?
Is the resistance of compressor
Is the resistance of compressor
discharge temp. sensor (T5) wrong
discharge temp. sensor (T5) wrong
according to Appendix 2?
according to Appendix 2?
Replace outdoor main PCB
Replace outdoor main PCB
Electrical Control System
Yes
No
Yes
No
Yes
No
Yes
No
No
No
F1
Reconnect the condenser
Reconnect the condenser
temp. sensor (T3)
temp. sensor (T3)
Replace condenser temp. sensor (T3)
Replace condenser temp. sensor (T3)
F2
Reconnect the wiring
Reconnect the wiring
Replace the outdoor ambient
Replace the outdoor ambient
temperature sensor (T4)
temperature sensor (T4)
F3
Yes Reconnect the wiring
Reconnect the wiring
Replace the compressor
Replace the compressor
Yes discharge temperature sensor
discharge temperature sensor
(T5)
(T5)
Troubleshooting
137