Strange one this!
If you push the right hand heater control up (normally the fan would start on low speed) mine is starting the air con fan instead! But the air con light is not coming on.
If you move the fan speed switch the normal heater fan does not come on atall.
If you have the heater control up so the air con is working, pressing the proper air con button does not stop it, but you can hear a solonoid type click when you turn it on and off from behind the glovebox area.

Any ideas?!

(It worked perfectly last week!)