Thank you Larry for your reply.

Having read in other threads that the system has an automatic protection against low refrigerant pressure, that is the EC light will remain on the moment you start the car with no possibility of turning it off. So I assumed that low pressure was not the problem as the ACC unit works the way it should be except for the compressor not turning on. I'm suspecting that when the dealer replaced the water pump they might have accidentally disconnected something as it was working before the dealer worked on the car.

Anyway, I will have the pressure checked ASAP.