Puzzled by dusk-to-dawn light....

Old 02-13-02, 04:58 PM
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Unhappy Puzzled by dusk-to-dawn light....


I'm hoping someone could shed a little light (please pardon the pun) about my dusk-to-dawn light.

This light is owned by me (not the local electric utility) and is located in my back yard. It has a photoelectric sensor which turns the light on when the outside light level decreases (usually at dusk or during inclement weather) and turns it back off when the outside light level increases (usually at dawn).

A week or so ago, I noticed that the light didn't turn on at dusk, so I assumed that the bulb had failed. However, I happened to wake up shortly before dawn a couple of days in a row, and found the light on. However, it didn't come on until many hours after sunset, instead of right at sunset as it normally would.

Any idea whether this indicates a bad bulb, or is the problem with the photoelectric sensor? Is it possible for a bulb to eventually come on, even if faulty?

Any input appreciated!
Old 02-13-02, 06:26 PM
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YOu didn't clarify if this dusk to dawn light is a high pressure sodium, mercury vapor, or other.

Charicteristics of these type fixtures is that they are ballasted bulbs. Often times the ballast gets weak, the bulb gets weak, the sensor gets intermittent or bad.

At times the sensor is aimed back toward a reflective wall covering causing the sensor to think it is daylight due to its own reflected light causing the light to shut back off unless it is very black outside.

I would suspect the bulb, then the sensor, then the ballast in that order.

The sensor can be tested by placing an electrical tape over the eye telling it that it is dark outside. This would confirm the use and conditions of that sensor if all works fine.

If it is a weak bulb you should see it come on half way then after a while kick off due to overheating trying to light the weak bulb. Then when the light cools back off it resets and starts to light again. If this is the case replacing the bulb should solve your problem. This I suspect may be your problem as you discribe.

Ballast may be weak causing it to overheat. I would suspect this at last resort.

Be aware that some inexpensive dusk to dawn lights have a ballast built into the bulb. If you have one of these then the cost of the bulb may be more than the cost of a new fixture.

Hope this helps


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