I noticed that the air conditioning works worse in automatic mode than before. The refrigerant level is fine. It works better in manual mode, but in the past, the automatic mode was always sufficient for me. I found the OBD code L0164 Lost Communication With HVAC Control Module, so I guess I was right, and there is indeed a malfunction. What should be replaced to fix this error? MY2011 TD4 S Manual
MY2014 Si4 HSE Auto
MY2017 C63S Coupe

Could be worth trying a second hand module. Be sure to replace the existing one with a similar code, its on a paper label at the back of the module. That's what I would try first.

I think the Code was U0164, it suggests that the car main systems are not able to talk reliably to the HVAC Module, which may not be the fault of that unit.

Before swapping out unit I suggest that you ---

Remove the Battery Leads and do a Hard Reset

Clear any remaining OBD Codes in system

Disconnect, Clean, and Reconnect Connections to HVAC Module

Check for any visible Damaged Cabling in that area

If you have other Lost Comms Failure Codes from other Modules, you will need to check the integrity of the MS CAN Network. (Page 3017 Repair and Wiring Manual)

From the Repair Manual
U0164-00 - Lost Communication with HVAC Control Module

Lost communication with climate control module
-Carry out the associated network test for this DTC using the manufacturer approved diagnostic system

PS Have you unplugged or disturbed any other module that may be on the same comms network lately? FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)