Wierd Electrical Problem

[Glenn9643]

We have an outdoor light, mercury vapor, very similar to this one:
Industrial Grade Mercury Vapor Security Light

Last summer I noticed that it would shut off at seemingly erratic intervals, after a while come back on, and eventually shut off again. I figured the light sensor was bad so I replaced it, but it continued to shut down. Finally I realized that when the central air conditioning came on it was causing the light to turn off.
Now it's winter and the light's shutdowns are more noticeable because we have more night hours I guess. Seems now that it is shutting down when the fan kicks in for our central gas furnace.
The AC unit is on a separate circuit, and the light isn't on the same circuit as the furnace fan either.
I've seen situations before where the house lights would dim when the AC kicked in, but we've never experienced anything like that.
Any ideas of what I might look for to resolve this problem?

 

[EddieWalker]

Two seperate lines, but they are affecting each other.

I had a similar thing happen with my internet connection. When we pluged in two space heaters, we'd lose our connection. One heater was fine, but anywhere in the house that we pluged in the second heater, it killed the connection.

We figured out that the computer was on a different ground inside the house than the dish was outside the house and was building up static electricity to the point it wouldn't work. I cut the ground from the outside dish and stoped the static electricity buildup.

In my situation, seperate grounds from two different main panels were building up static electricy and somehow the space heaters increased this. Now that I have it all on the same ground, there are no more problems.

I don't know how this could help, but it was a very odd electrical problem that I fixed because another poster here mentioned static electricity, and I was able to figure it out because of that.

Good luck,
Eddie

 

[JoeL4330]

Two seperate lines, but they are affecting each other.

I had a similar thing happen with my internet connection. ...
We figured out that the computer was on a different ground inside the house than the dish was outside the house and was building up static electricity to the point it wouldn't work. I cut the ground from the outside dish and stoped the static electricity buildup....

In my situation, seperate grounds from two different main panels were building up static electricy ...

Good luck,
Eddie

"Static electricity"? You may want to google "ground loop"

 

[Glenn9643]

OK, I did the suggested google on "ground loop". Everything I read indicated that it resulted in audio problems or maybe TV reception problems from the interfering signal. We don't have this problem.
The only thing noticeable is the light going off when the furnace fan turns on or in summer when the AC turns on. The furnace fan isn't a heavy load I don't think.
The light is on a metal pole mounted on a steel base, hinged for lowering. I believe that I attached the ground wire in the romex to the steel frame when I installed it but am not certain.
This problem wasn't noticed for about three years, and seemed to begin last summer.

 

[DieselPower]

Have you checked the electrical connections in the light housing, specifically the wire nut connections to make sure they don't have the green nasties growing in them? You might have a high impedance situation due to corrosion and it's making the problem happen more often.

 

[Glenn9643]

I went over all that a few months back when I had it lowered to replace the lighting sensor. Also gave it a good cleaning to remove the dead bugs.

 

[bones1]

Have you checked the electrical connections in the light housing, specifically the wire nut connections to make sure they don't have the green nasties growing in them? You might have a high impedance situation due to corrosion and it's making the problem happen more often.

Most probably.If not you could run a temporary line,heavy cord to the light and see if the problem persists.If the light still malfunctions with the temporary connection It might be time for an electricians opinion.

 

[Buckeye_Jim]

Have you operated the fan only control on your furnace? Turn the fan on, the light goes off? Turn the fan off, the light goes on? Is it consistent? It may just be a weak bulb.

Jim

 

[Glenn9643]

Thanks for all the input. I believe I've found the answer and will have to work on the problem more now.

"A lamp which is cycling - starting, warming up, then turning itself off - is probably overheating due to a bad bulb or ballast. A thermal protector is probably shutting down the fixture to protect it or the arc is being extinguished on its own. However, make sure that it is not something trivial like a photoelectric switch that is seeing the light from the lamp reflected from a white wall or fence and turning the fixture off once the (reflected) light intensity becomes great enough!"
Sci.Electronics.Repair FAQ: Notes on the Troubleshooting and Repair of Small Household Appliances and Power Tools

When I lowered it and replaced the light sensor I had a new bulb but didn't replace it because the old one seemed to be working, but the new sensor failed to correct the problem. Since I have the new bulb I'll try that this afternoon. Hopefully the ballast is OK...

 

[tallyho8]

Mercury vapor, metal halide and high pressure sodium lights will go off for a while then come back on when the bulb is bad. However, this doesn't sound like your problem because you state that the light goes out when another electrical appliance comes on. These lights will go out temporarily on a voltage drop. Whenever any motor starts is uses a surge of electricity while starting and if your wiring isn't sufficient for your usage, there will be a voltage drop when the motor starts making the light go out temporarily. There are many things that can cause deficient wiring problems. Circuits may be overloaded, corrosion may be present, wiring may be inadequate, etc. You can test for a voltage drop using a volt meter on the circuit while the appliance starts. It can be just a slight drop for a fraction of a second and this is enough to make your light go off. Most often, running a wire for too long a distance to the light or using too small a wire is the problem, though the problem may be anywhere in your electrical system.