Mitsubishi PUHY-EP250 - Error Code [4121]

[7-6 Error Code Definitions and Solutions: Codes [4000 - 4999] ]
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HWE12050 GB
7 Troubleshooting Using Error Codes
7-6-6 Error Code [4121]
1. Error code definition
Function setting error
2. Error source, cause, check method and remedy
Error source Cause Check method and remedy
Outdoor unit (1) Dip switch setting error on the control board Check the SW6-1 setting on the control board
(2) Connector connection error on the control
board
Check that nothing is connected to the connector
CNAF on the control board.
(3) Control board failure Replace the control board if no problems are
found with the two items above.