Outdoor lighting issue.

I have an outdoor security light on a utility pole provided by the power company that has been in place for around 50 years. A few months ago I woke in a pitch-dark room and it took me a few moments to realize it was because the light outside was off. It stayed off for a couple of nights, then came back on for a couple more, then went off and stayed off. I figured that the bulb needed changing–it was last done 10 or so years ago–but I needed to clear branches for a path for the bucket truck before I called the power company and hadn’t got around to it yet. Then a few nights ago I noticed that it was on again without any intervention. There had been some rain earlier that day, but nothing as he vy as had fallen other times in those months, and debris covering the photodetector would have made it stay on not off anyway. So any guesses per: what’s up with that?

Maybe the leaves on the branches are reflecting light back at the detector? When wet the effect might be more intense. Just a guess.
Trim the branches and see if just that works, before doing anything else.

So the photodiode and control circuitry is 50 years old? If so, I am surprised (RE: impressed) it’s lasted this long.

The house I inherited was built in 64. I was born in 72. The light was installed some time between those dates (maybe chosen as an option when electricity was first connected?) I don’t specificly remember any maintenence during my childhood, just the bulb replacement 10 or 12 or so years ago.

No circuit lasts forever. And the temperature cycling doesn’t do it any favors. Am guessing something simply failed in the circuitry.

Oh, and I meat to say “photoresistor,” not “photodiode.” As old as it is I am guessing it uses a CdS photoresistor.

That is an impressive life span for that light. We have 3 lights provided by the power company, ( well, actually we pay a small fee, monthly, just thinking these lights have cost a small fortune! hmmmm?) We have lived here 20+ years and I think they have replaced the fixtures at least twice and one just cannot keep a bulb working. I don’t know how many times they replaced that bulb. A bunch.

I’ll pretend it’s a HPS fixture and say maybe a failing ignitor. Is it possible the lamp is cycling throughout the night and your only catching it when it’s in one state or the other every couple nights? Also might be water in the photocell doing wonky stuff.

No, the cycle was around 2 nights off, around 2 nights on, around 2 or 3 months off, and as of now around 3 or 4 nights on. Googling for photos of HPS fixtures, it looks pretty similar to this one.
ETA: that link mentions the light color–when a digital camera is on the “sunlight” white balance, the light shows as strongly green.

Are you paying a surcharge on your utility bill for the light? Did you contact the power company that provided the light?

$9.00 a month, and from the OP “I figured that the bulb needed changing–it was last done 10 or so years ago–but I needed to clear branches for a path for the bucket truck before I called the power company and hadn’t got around to it yet.”

HPS lights are notable for their crappy yellow light and very long lifetime. Very common in street lighting.
Normal end of life lamp cycling happens in intervals of a few minutes continuously until complete failure or replacement.

Could be a hand full of things. Bad connection, bad ignitor, bad photocell… Hard to say with moisture present, and possibly temperature swings.

I’ve seen a couple times lights shining into each other’s photocells and which ever one was the more sensitive or had the shorter delay lost for the night.

Oops. Sorry, I missed that.

I’m thinking a 40+ year old yard light is most likely a mercury vapor. That could give a green tint if a cool white clear bulb is used. I’m sure a 10 year old bulb is due for replacement. Replacing the associated snap in light sensor would be cheap insurance if it is truly an original part. Upgrading to an LED fixture is also an option. I am not sure of a LED replacement bulb for a mercury HID fixture.