Motion activated lights

[Daryl]

Got a mystery. We've had this house for about five years. On one side in the back there is a motion activated light, I don't know the brand. It never fails that about this time of year the light starts being erratic and eventually stops turning on. I can get right under it and jump around as much as I like, but to no avail. Just a couple weeks ago I couldn't stick my head around the corner with out it turning on. Like I said, this is a seasonal deal.
During winter I make a few plans for improvements and that light is on my list. OK OK it's on my wife's list. But, every year towards the end of March, it will start working again, actually, about the middle of summer it will turn on during the day if somebody goes around there. Needless to say, I have never done anything to it except replace the bulbs, but they weren's burned out.
So, any Ideas?

[LCHIEN]

Get a new one?

[thrytis]

Have you examined the sensor carefully to see if it was fogged up on the inside with moisture or something? I don't know where you are located, but do you have a weather change this time of year that could attribute to the failure?

[gjbivin]

Could the Sun be shining on the sensor? That would explain the seasonal changes.

[LinuxRandal]

Dad had a cheapy that wasn't well sealed. Moisture in it screwed up the timing. He tried to replace just that part and found it MUCH cheaper to replace the whole fixture.

The only other thing I can think of would be the angle, as not all have the same range or angle of sensing.

[Daryl]

The sun don't shine too much at night here so I really don't give much thought to the sun's angle. I'll probably take it down and just put up a switched light.

[vaking]

A lot depends on your climate, temperature and humidity. Most motion detectors react on "moving heat", they recognise a person moving from a tree moved by the wind by looking for temperature difference. Is this the time of a year when the outside temperature is "just comfortable", not too hot and not too cold? That would mean your outside temperature is about same as temperature outside and sensor fails to detect your motion. Replacing the sensor might not help then, it is not defective.

[offthemark]

There are several things that could be the problem. You can get motion lights for less than $20. Just replace it and quit worrying about it.

[Daryl]

A lot depends on your climate, temperature and humidity. Most motion detectors react on "moving heat", they recognise a person moving from a tree moved by the wind by looking for temperature difference. Is this the time of a year when the outside temperature is "just comfortable", not too hot and not too cold? That would mean your outside temperature is about same as temperature outside and sensor fails to detect your motion. Replacing the sensor might not help then, it is not defective.

This seems to be the best reasonable explanation I've gotten, thanks vaking.