Window Sensor, Volvo V70?

I have an 04 Volvo V70 and have just had the windows tinted (with film), ever since this has been done the alarm on the car goes of a random times. I know the guy I purchased it from very well and he has had it for 3 years or more and never a problem. Its started happening ever since I had the windows done. The rear windows have 2 small sensors in the window so if the glass was smashed it would set off the alarm, I have taken off the black plastic caps to have a look, pushed them on etc but it still goes off. Is there anyway this can be fixed or not have these connected but still have the alarm on for the main part of the car. Can you help?

David Smith
May 2010