I've just changed a PIR on my alarm system today and have inadvertently broke off the sensor adjustment screw. How critical is this part and if I'd fit it without it will I have problems. the part resembles a tiny plastic Phillips screw head and it literally snapped off as I touched it. the sensor is a Honeywell activ8 single channel quad PIR. If I have to buy a new one I will but hopefully I may get away with it. Many thanks in advance.