Carrier X-POWER Series Service Manual page 150

R410A DC Inverter Series
4.3 E4: Ambient temperature sensor (T4) error/ (Display on faulty unit, all the ODU in standby)
E4: Ambient temperature sensor (T4) error
Connecting wire between
sensor and main control board
is loose
No
Sensor is short circuit or disabled
(Using a multimeter to measure
resistance, if the resistance is too
small, the sensor is short circuit, if
the resistance in certain temperature
is not consistent with attached table
1, the sensor is disabled)
No
Outdoor main control board is
damaged
168
Yes
Fasten the connecting port
Yes
Replace the sensor
Replace the outdoor main control board
Carrier service manual
Troubleshooting