Cars A/C seems to come on with no A/C being on ,or when its on screen only.The A/C engine fan seems to be running alot of the time,could it be a switch/relay?
Stating the obvious, is the indicator light illuminated on your control panel? Can you switch the light on and off, (using the button)? Usually if a relay or switch fails it makes the function fail, ( not constant) You could try replacing the relay, its probably under the steering wheel area, or under the bonnet. It should be clearly marked.
Havn't had the car long,and it camer without an owners guide,so i'm not sure where the relay is at present,if its marked i'll find it.Must get an Haynes manual.