What car is this ?
Climatronic isn't getting analog RPM signal from ECU anymore, it can't work without seeing engine RPM (or at least that the engine is running).
About the brake switch. Either your wiring to the ECU is wrong, or the brake light switch itself is the incorrect one. You need one with 4 wires (terminal X, terminal 30, normally closed (NC) contact and normally open (NO) contact). ECU needs to see both NC and NO contacts to be happy. ABS needs only NO contact and DSG see's it through CAN bus, that's why no faults there.