Electrical – Why aren’t the PIR security lights working through the window

Typically an exterior light will have a cable directly from the switch to the light soley for the purpose of switching. This is unlike some electrical boxes you will find in your interior where there are circuits branching off within the box, or where power might come in at the ceiling and then a cable is run to the switch.

Assuming this is the case, once you disconnect it the old switch and light, connect the hot and neutral (black/white) together with a wirenut on both ends. This is a good way of indiciating that it is no longer in use, and if someone were to mistakenly connect it again, it would short out and trip the breaker. If it is not wired in this manner you will need to be a bit more careful with what you disconnect and tie together.

On the outside, if your new light fixture is not being mounted to the same electrical box then you would want to cap the box with a weather tight cover.

I think your strategy of making a cone out of aluminum foil was on the right track, but your choice of material was not. Think about what happens when you put various materials in the microwave. Paper, glass, ceramic: no effect, these will be ineffective. Aluminum foil: unintended consequences, do not use. Then consider what the microwave itself is made out of. You are essentially making the window (which is a person window, the negative image of a sensor window) This suggests the use of a grounded metal mesh or foam. Locally in NYC, the SpyStore sells copper-nickel mesh fabric for unstated purpose. You should also be able to find self-adhesive EMI/RF shielding foam at various industrial suppliers such as McMaster-Carr. You will want to wire either material to ground. I would start by trying to disable the sensor completely by this method (of covering it with grounded metal mesh or foam.) Then open a small aperture in the opposite direction of the corridor. Increase the size of the aperture until the functionality is as you desire. Use white self-adhesive paper label stock cut slightly larger than your masking material to return the sensor to an all white appearance if that is important.