Error Code Definitions And Solutions: Codes [3000 - 3999]; Error Code [3121] - Mitsubishi Electric HP120TNU-A Service Handbook

[7-5 Error Code Definitions and Solutions: Codes [3000 - 3999] ]

7-5

Error Code Definitions and Solutions: Codes [3000 - 3999]

7-5-1

Error Code [3121]

1. Error code definition
Out-of-range outside air temperature
2. Error definition and error detection method
When the thermistor temperature of -28°C[-18°F] or below has continuously been detected for 3 minutes during heating op-
eration (during compressor operation), the unit makes an error stop and "3121" appears on the display. (Use the OC therm-
istor temperature to determine when two outdoor units are in operation.)
The compressor restarts when the thermistor temperature is -26°C[-15°F] or above (both OC and OS) during error stop. (The
error display needs to be canceled by setting the remote controller.)
Outdoor temperature error is canceled if the units stop during error stop. (The error display needs to be canceled by setting
the remote controller.)
3. Cause, check method and remedy
Check the following factors if an error is detected, without drop in the outdoor temperature.
Cause
(1) Thermistor failure
(2) Pinched lead wire
(3) Torn wire coating
(4) A pin on the male connector is missing or
contact failure
(5) Disconnected wire
(6) Thermistor input circuit failure on the control
board
<Reference>
18
- chapter 7
Short detection
TH7 110 C [230 F ] and above (0.4 k ) -40 C [ -40 F ] and below (130 k )
Check method and remedy
Check thermistor resistance.
Check for pinched lead wire.
Check for wire coating.
Check connector.
Check for wire.
Check the intake temperature of the sensor with the LED
monitor.
When the temperature is far different from the actual temper-
ature, replace the control board.
Open detection
HWE18220_GB