Alarm problem

[HollyDog]

I have 2017 Mercedes E class cabriolet, the alarm is going off, but only when the car has been stood in the SUN for 3 to 4 hours. I have removed all items out of the car so no loose objects left inside. If I switch the internal sensors of the alarm doesn’t go off !!!
Mercedes assist have been out to the car and couldn’t find any fault codes and checked the battery which is in great condition
The alarm has never gone off through the night and on a normal British Day never goes off
Any help and suggestions welcome

 

[alecmascot]

convection air currents are detected by the interior sensors.

 

[wrdcc01]

Try closing all the air vents before you arm it.