How to solve mystery of unrelated switch allowing function of unreliable switch (DIY)

[DianeG]

I'm new here, a DIY member. I hope I'm in the right place.
About 18 years after it was built, the following problem started with the light switches for our foyer light. The diagram shows the setup of switches on the front half of our modular house.

The problem is that sometimes, maybe once a week or less, the foyer light will not turn on/off at either the front door or hallway location. (Sometimes trying the second switch location will work, but less so lately.) What always works is turning off/on the porch light switch -- then the foyer light will turn on/off. The porch switch is only at the front door (a single, not multi-way) and should not be related to any other switch. How could it affect the working of the 3-way foyer light? What can we check? It looks fine inside the boxes. (My husband is an engineer working in the construction business, so we have a clue about doing these things.)

When the foyer light started having the problem, we replaced the switches; it did not help --we checked again for tightness and placement after replacing it. The foyer light also (rarely) blinks off while turned on and seems to require unusually frequent bulb changes. The blinking is not related (by observation) to times that it will not turn on/off normally. We plan to replace the fixture, but it doesn’t seem that a problem with the fixture would cause the porch light to affect operation. (Note that the scenario is usually turning off the porch light since it’s almost always left on, due to having a light sensor.)

I am concerned about something being loose inside the wall somewhere since everything in the boxes seem fine.


Thanks!

 

[mainline]

I'm new here, a DIY member. I hope I'm in the right place.
About 18 years after it was built, the following problem started with the light switches for our foyer light. The diagram shows the setup of switches on the front half of our modular house.

The problem is that sometimes, maybe once a week or less, the foyer light will not turn on/off at either the front door or hallway location. (Sometimes trying the second switch location will work, but less so lately.) What always works is turning off/on the porch light switch -- then the foyer light will turn on/off. The porch switch is only at the front door (a single, not multi-way) and should not be related to any other switch. How could it affect the working of the 3-way foyer light? What can we check? It looks fine inside the boxes. (My husband is an engineer working in the construction business, so we have a clue about doing these things.)

When the foyer light started having the problem, we replaced the switches; it did not help --we checked again for tightness and placement after replacing it. The foyer light also (rarely) blinks off while turned on and seems to require unusually frequent bulb changes. The blinking is not related (by observation) to times that it will not turn on/off normally. We plan to replace the fixture, but it doesn’t seem that a problem with the fixture would cause the porch light to affect operation. (Note that the scenario is usually turning off the porch light since it’s almost always left on, due to having a light sensor.)

I am concerned about something being loose inside the wall somewhere since everything in the boxes seem fine.


Thanks!View attachment 121343

Are the lamps Led ?

 

[littlespark]

If i understand you.... when the switches for the foyer cease to work, turning the porch off and back on basically "resets" the foyer switches, and they start to operate again properly?

Not the switches themselves, as youve changed them already....

Im wondering if the sensor on the porch light is somehow affecting how the other lights work?

You could try leaving the sensor turned off for a period of time and see if the foyer switches behave

 

[DianeG]

Thanks for the replies. My replies:

The porch light does not have to be turned both off and on to help -- just one is enough, usually off, since that switch is usually left on.

The foyer light bulb was incandescent and is now LED. I don't remember if that has made a difference -- I could put in an incandescent bulb again. While I can see how that could make a difference in the fixture (a cheap basic one that came with the modular house), the mystery seems to be why the porch light would affect it!

I could try turning off the porch light sensor. Would you suggest also leaving the porch light switch off? I'm still curious about how they could be related.

The foyer light (both switches) is the only problem so far, and the porch light switch allows it to function when it doesn't work. I have not tried leaving other lights on in various combinations. It happens so rarely it would take a while to learn something.

 

[mainline]

Thanks for the replies. My replies:

The porch light does not have to be turned both off and on to help -- just one is enough, usually off, since that switch is usually left on.

The foyer light bulb was incandescent and is now LED. I don't remember if that has made a difference -- I could put in an incandescent bulb again. While I can see how that could make a difference in the fixture (a cheap basic one that came with the modular house), the mystery seems to be why the porch light would affect it!

I could try turning off the porch light sensor. Would you suggest also leaving the porch light switch off? I'm still curious about how they could be related.

The foyer light (both switches) is the only problem so far, and the porch light switch allows it to function when it doesn't work. I have not tried leaving other lights on in various combinations. It happens so rarely it would take a while to learn something.

Try changing the lamp to incandescent, as it's the easiest thing to do first.

Induced voltages and electronics can cause some strange happenings.

 

[DianeG]

Try changing the lamp to incandescent.

Done. Thanks. We probably won't know anything for a week or longer since it rarely does this. I'm thinking I should keep the porch light on with the sensor as usual, so we're testing one thing.

 

[mainline]

Done. Thanks. We probably won't know anything for a week or longer since it rarely does this. I'm thinking I should keep the porch light on with the sensor as usual, so we're testing one thing.

Let us know how you get on.

 

[DianeG]

I'm still hoping to get some sort of explanation of how the porch light switch could possibly affect the function of the foyer light. Other than being in the same box, they shouldn't interact at all. The fact that they do is disturbing since it seems to suggest a problem located beyond the box. I suppose it makes sense that the foyer lamp type would affect the foyer fixture performance, but not that it would have anything to do with the porch light switch. I'm happy to leave the lamp change for now, just in case.

 

[mainline]

I'm still hoping to get some sort of explanation of how the porch light switch could possibly affect the function of the foyer light. Other than being in the same box, they shouldn't interact at all. The fact that they do is disturbing since it seems to suggest a problem located beyond the box. I suppose it makes sense that the foyer lamp type would affect the foyer fixture performance, but not that it would have anything to do with the porch light switch. I'm happy to leave the lamp change for now, just in case.

Led lamps need very little current to make them glow/flicker this could be caused by induced currents in nearby cables.