I came home from work to find that the house alarm had gone off. It was shown that it was triggered from the PIR in one of the bedrooms. The PIR was constantly flashing wether there was anything passing in front of it or not and subsequently it was not possible to set the alarm unless I omitted that PIR. On the assumption that it was faulty PIR I bought a new one and replaced the old one. Now I find that none of the internal PIRs are working, the front and back door ones do work. What to do?