# I have a high pressure sodium vapor lamp that is going onand off



## mldollins (Jun 21, 2008)

Is it the sensor or the bulb itself? It turns on but it does not seem as bright and then in about 5 minutes it goes off.


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## Sawmill Jim (Dec 5, 2008)

Bad Ballast some call it a transformer :shrug:


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## mldollins (Jun 21, 2008)

This thing is around two and half years old. I wonder if it is best just to replace the whole thing.


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## tyusclan (Jan 1, 2005)

mldollins said:


> This thing is around two and half years old. I wonder if it is best just to replace the whole thing.


It's easier, and it won't be a whole lot more expensive. 

There's a multi-voltage kit that you get to fix them. You have to get the correct wire for the voltage that you have, and there are several other wires that all have to be connected correctly. All unused wires have to be taped or capped off separately.

There are instructions and a schematic to tell you how to do it, but they can be a little daunting if you're not familiar with them.


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## sammyd (Mar 11, 2007)

put a new bulb it it.
9 times out of 10 a new bulb will fix the problem.


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## Old John (May 27, 2004)

Yes, but sometimes the Daylight sensor, that turns the bulb off when there is Daylight goes bad, and needs to be replaced. I bought a new bulb for ours. And the Daylight Sensor was bad. But, I do have a spare bulb, on hand now.


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## mldollins (Jun 21, 2008)

...replaced the starter and same problem. I will just buy a new one. At walmart they're 59 bucks. If I buy a new bulb, its around 30+.


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## edmonds (Dec 19, 2008)

Remove the bulb and leave the light off. Its probably unshielded and isn't helping as much as you think. You might be surprised how well you can see without light glaring into your eyes, which reduces contrast and makes it harder to see (think of on-coming car headlights). If you feel like you gotta have it, put up a shielded, motion sensor light.


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## mldollins (Jun 21, 2008)

I just purchased a metal halide lamp. Its near impossible to find a ballast for the thing. A bulb would have cost 20 bucks(from menards). I do kind of think it might have been the bulb, but you never know. ....oh well....


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## tyusclan (Jan 1, 2005)

sammyd said:


> put a new bulb it it.
> 9 times out of 10 a new bulb will fix the problem.


If the bulb is coming on and off the bulb cannot be bad.


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## farmerpat (Jan 1, 2008)

You may want to call your utility company about it. Where we live, if the sensor or anything OTHER than the bulb goes wrong, they come out and fix it for free or the cost of the part.


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## Oldcountryboy (Feb 23, 2008)

What kind of light fixture are we talking about? A pole light? A outdoor wall pack light? ????

If it's a pole light it could be either the transformer or the photo cell on top of the fixture. Put a peice of black tape over the eye of the photo cell and see if the light stays on all the time. If it continues coming on and off then it might be your transformer. If the light comes on and stays on, then you might need to turn the photo cell in a different direction as you might be getting a light reflection back to the photo eye which will cause it to keep turning itself off. 

Still unsure, then replace the photo cell first as they use to cost only around $10 but with the inflation it is probably higher now. If that doesn't work then it is probably the transformer inside the fixture. Which might cost you about the same price as a new light fixture.


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## sammyd (Mar 11, 2007)

tyusclan said:


> If the bulb is coming on and off the bulb cannot be bad.


 These aren't regular lightbulbs ya know.
I have been in industrial maint for over 20 years and it's been my experience that 9 times out of 10 if I am called to a light that is going on and off I can replace the bulb and fix the problem.


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## blufford (Nov 23, 2004)

I'm pretty sure when that happens it means an earthquake is going to happen.


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## CindyOR (Jul 23, 2004)

We've had this happen and it turned out to be the sensor. This is a pretty easy fix. Just take the old sensor out (ours was located on the top of the light and just pulled off like unplugging something) and take it with you because there are others that look very similar and it can be confusing to get the exact right one. One thing you might want to try first - clean the top of the sensor off. I did that the first time this happened and it lasted 2 more years before doing the on/off thing again.

In 14 yrs we've changed the bulb twice, cleaned sensor once and changed the sensor once. Most of these lights last a long time, so 2-1/2 yrs is really nothing in the terms of how long they should go without a problem.

I'd try cleaning the sensor with a damp cloth and see if that gets you going again. If not, pull the sensor and replace it and see if that works. 

I agree - if the bulb is going on and off, it probably isn't the bulb.

CindyOR


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## arabian knight (Dec 19, 2005)

Yes I would say the sensor maybe the problem. I have notice driving around at night that in one of my vehicles the headlights are not aimed. And I have noticed the some Street lights going out as I approach if they have that sensor pointed wrong. lol
SO is this where there might be a lot of traffic? Or does this happen any time any place no matter what time of day or night with no traffic affecting it?


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## tyusclan (Jan 1, 2005)

sammyd said:


> These aren't regular lightbulbs ya know.
> I have been in industrial maint for over 20 years and it's been my experience that 9 times out of 10 if I am called to a light that is going on and off I can replace the bulb and fix the problem.


Yes, I know that they're not 'regular' light bulbs. I've been in maintenance for many years myself, and I've rebuilt more of these than I can count. I've NEVER had a bad bulb come on and off.

I've also never had a bad photocell come on and off. They either stick on or they stay off. The ONLY thing I've ever found wrong on a light coming on and off is the transformer.


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## tiogacounty (Oct 27, 2005)

tyusclan said:


> Yes, I know that they're not 'regular' light bulbs. I've been in maintenance for many years myself, and I've rebuilt more of these than I can count. I've NEVER had a bad bulb come on and off.
> 
> I've also never had a bad photocell come on and off. They either stick on or they stay off. The ONLY thing I've ever found wrong on a light coming on and off is the transformer.


 2nd this. Generally "thermal-cycling" is the issue where a transformer is overheating as it fails, tripping off then returning to service as it cools.


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## mldollins (Jun 21, 2008)

I did open the old one up and saw the transformer. But it is likely it would cost the same as a new light. I'm not sure where you would begin finding a transformer.


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## tyusclan (Jan 1, 2005)

mldollins said:


> I did open the old one up and saw the transformer. But it is likely it would cost the same as a new light. I'm not sure where you would begin finding a transformer.


You have to get them at an electrical supply. As I said in an earlier post, they come in a rebuild 'kit' with the capacitors and everything else you need to make it work.


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## Billin (Nov 24, 2009)

It's called cycling and its normally the swan song for the lamp. A new one should solve the problem. Lamps shouldn't be overly expensive, depending on the size.


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## Joshie (Dec 8, 2008)

We've recently had the same problem. Light would work then it wouldn't. Light went on and off several times each night for a while. Then, for a couple of weeks, the thing worked perfectly. It started the cycling and after a couple of days it went out. It's been out a couple of weeks now. I'd really like to get it fixed. Just don't know who to call to fix it. Concerned about the cost.


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## sammyd (Mar 11, 2007)

tyusclan said:


> Yes, I know that they're not 'regular' light bulbs. I've been in maintenance for many years myself, and I've rebuilt more of these than I can count. I've NEVER had a bad bulb come on and off.
> 
> I've also never had a bad photocell come on and off. They either stick on or they stay off. The ONLY thing I've ever found wrong on a light coming on and off is the transformer.



At the end of life, high-pressure sodium lamps exhibit a phenomenon known as cycling, which is caused by a loss of sodium in the arc. Sodium is a highly reactive element, and is easily lost by reacting with the arc tube made of aluminum oxide.

As a result, these lamps can be started at a relatively low voltage but as they heat up during operation, the internal gas pressure within the arc tube rises and more and more voltage is required to maintain the arc discharge. As a lamp gets older, the maintaining voltage for the arc eventually rises to exceed the maximum voltage output by the electrical ballast. As the lamp heats to this point, the arc fails and the lamp goes out. Eventually, with the arc extinguished, the lamp cools down again, the gas pressure in the arc tube is reduced, and the ballast can once again cause the arc to strike. The effect of this is that the lamp glows for a while and then goes out, repeatedly.


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