Headlight "sensor" on DRL equipped models

Does anyone know exactly where the "auto headlight" sensor is on the Achieva equipped with day time running lights? I am thinking it in in the defroster vents on top of the dash and this is also what I was told. Unless the sun is high in the sky, or there is a "bright overcast", the headlights will automatically illuminate easily on my mothers 97 Acheiva. Not a big deal if they were to always stay on, because we often run with the headlights on anyway, but they are turning off and on, depending upon light outside and I do not want people to think that it is a warning, nor do I think it is good for the bulbs. The car does have a state inspection sticker on the passenger side of the windshield, which does block some of the light, but I have seen other Achievas with DRLs with the same sticker, with only the DRLs on. I am thinking maybe this sensor is covered with dirt or something. I have also seen others with the lights on, with the stickers as well, but it seems to be random. Any info appreciated.

I found out that it is indeed in that defroster vent on the passenger side. We removed that sticker and it is working properly now.