OK, so I have just got back from having the A/C rechecked. The system hasn't lost any pressure over the week since it was put onto the machine and regassed etc, so the mechanic connected up his diagnostic box of wizardry and the following was the outcome.

Fault Code E723 No message (condensation sensor). OX2DI Receiver Integrated Automatic Heating Aircon system Transmitter Roof Function Centre

We, (well I was watching :-) ) removed the cover away from behind the rear view mirror and found a sensor, he then removed the cover of the sensor very carefully and there was a circuit board (this is now more my territory), which we are guessing is a combination of the auto light sensor and the A/C.

Baring in mind that he is not a BMW specialist, but he is a qualified A/C engineer, I went there because they have proven to me over the years that they are a genuine company. I have now come home to see what I can find out, while he can get on earning some money with the queue of customers that were drinking all of the free coffee in the waiting room, and I could do some investigating and hopefully get an answer to my question.

Before I go and part with some of my hard earned, has anyone experienced an issue with this sensor before? Do they fail, or like other sensor type faults, is there something else that we should be looking at that could cause this fault? I could just order the new sensor from BMW, but knowing them and their pricing strategy, I would hate to hand over an arm and a leg, only to find that the fault was a penny washer.

Something else that I have noticed since getting back home, the green light on the snow flake button has started to flash, even after turning off the control panel by reducing the fan speed to lower than low, before, it was either on or off before, I am guessing the flashing light is because of trying to cancel the error code, the system is now showing that there is a fault.