Heat triggers alarm?

With the recent hot weather, if the rear of the car is in full sun for any length of time, the alarm triggers, the doors unlock and the back window drops as if opening the door. The central locking sounds a fault beep on the horn. The back window will go right down from the interior switch but not up. Sometimes the fault will clear by opening and closing the rear door. As soon as the temperature drops or if the car is moved to shade the rear, everything returns to normal. Any ideas?

faulty switch on your removable hardback. right hand side on the slopy bit IIRC

Sorry, should have stated 04, td4 hse estate.

More information. The car thinks the rear door is open. The door open light is on when the ignition is on but the rear glass doesn't drop. The alarm will not reset unless the door is opened and closed. I would have expected the rear glass to drop if the sensor triggered but it seems this only happens when the lock is operated. All points to the door open sensor so, where is it? Any idea of a part number and is it a DIY job?
Thanks for any info, Terry.

you need .....Dann!

Quite possibly.

hopefully he'll look in soon. He seems to have solved most of these taildoor/window issues before so without wishing to sound unhelpful it's better to get advice from him.

Hi Terry, Been a bit tied up getting a clients car to Italy but hey back at base now and read your post and thinking probably O.k now as it's colder in U.K suddenly?

The CCU thinks the door is open.

The solenoid which operates the tail door latch when you press the handle also moves a latch position sensor, this device is adjacent to the solenoid unit. My guess is that the heat building up inside the tail door is causing this component to send a false 'door open' signal to CCU due to expansion of small moving parts which are subsequently jamming. My next step would be to remove door panel and peel away moisture membrane to apply light penetrating oil to all moving parts in latch/solenoid area.

Good luck.D..

Brilliant, I will try that next week and hope we have some more hot weather to test the result. Will post one way or the other. Thanks, Terry.