Thread: Flashing lights on dimmer switches

I work on the plumbing side, but was wondering what would cause lights on a dimmer switch to start to flash - nearly strobe - while in a mid position on the switch on occasion, but work fine at other times?

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Defective dimmer.

Possibly defective electronic components or circuit board.

May have been used for too high wattage, may be other causes.

Not that easy. Dimmers have been replaced. Occurs on more than one light/circuit.

Originally Posted by Mike Cudahy

Not that easy. Dimmers have been replaced. Occurs on more than one light/circuit.

"Dimmers have been replaced."

With same brand? Could be a defective lot of dimmers?

"Occurs on more than one light/circuit."

More than one light, okay, but are you sure they are on more than one circuit? I.e., you could have several dimmers, in different rooms, but all on one circuit.

My next guess would be (if dimmers are a different brand and not of the same possibly defective lot - as in 'manufacturing lot) would be a nail/screw through an NM cable, but ... if you are having this on different circuits, that would be less likely (although still possible being as many electricians bundle their wires). A nail/screw through an NM cable on one circuit could effect multiple lights and dimmers.

Try this: remove all but one dimmer, does the problem go away. Now add another dimmer and make the first dimmer a switch, is the problem still gone? Does the problem stay gone at each location when only one dimmer is installed?

Now add in a second dimmer and repeat above.

You are trying to find out if the dimmers are somehow interacting and interfering with each other.

Loose neutral?

Originally Posted by Scott Patterson

Loose neutral?

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Ditto.
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If at the Service entrance.

Motor loads on the system ( washer, Dryer, AC, ect ) will make this condition more apparent and show up on other lighting.

MAKE SURE THE BULBS WERE NOT REPLACED WITH COMPCT FLUORESCENT BULBS. I'VE SEEN COMMERCIAL INSTALLATIONS WITH THIS PROBLEM. BULB DOESN'T HAVE ENOUGH JUICE TO STAY LIT.

Hello,

This is my first post and since I was an electrician for 26 years before becoming a home inspector I'll throw my 2 cents in. I am wondering what kind of lighting you are writing about. Are they hi-hats or recessed? If so, there may be a faulty thermal cut-out on the fixtures in question. Sometimes a faulty cut-out will tend to flicker before going out or steadying itself. If this is happening on multiple fixtures, were they all installed at the same time? If so, the homeowner may have received a faulty lot.

If the fixtures in question can be accessed, they can bypass the thermal cut-out with a test bulb wired in unison with the faulty fixture. Then they can try the dimmer again. If the test bulb flickers, I would look for a faulty neutral in the circuit. If it does not flicker but the fixture does, I would expect it to be the thermal cut-out. I would also make sure that the dimmers in question are grounded.

I hope this helps.

Originally Posted by Mike Cudahy

while in a mid position

This is what throws me and why I don't think it is the lights themselves, or a loose neutral, "mid position" would not do that with a loose neutral, higher or lower positions would make the condition worse (taking more load or less load) by affecting the unbalanced condition of a loose neutral.

Similarly with being the TC in recessed lights.

At least ... "I would think" the above.

By the way, you can have faulty TCs in recessed lights. I've had them in years past when I managed two lighting fixture showrooms and when our electricians installed them.

I installed two 4" round recessed over our sink in our house here a few months back, now here it is summer (hot attic) and the lights do not work during the day - but do at night when the attic cools ... faulty TCs on the lights, I'm going to have to abandon them (they are IC rated recessed lights and I kept the insulation back 3" anyway, guess I either need to cover them with insulation (to keep them cooler) or by-pass the TCs and keep the insulation back (like it is) as though there were not IC rated (because they won't be any more if I abandon the TCs).

I might try just covering them with insulation first: 1) it's easier; 2) they are IC rated and are designed for that; 3) it's easier; 4) it's easier.

OK, it's my own house, and we have dozens of lights on dimmers - in closets even...... One set of lights that flashes is bathroom high hat recessed incandescent- but the usual flashing comes from my outdoor coach lights - also normal incandescentbulbs.

On of my EE buddies suggested some cross-talk between dimmers, but I can't figure what changed to start the problem - I even changed the suspect bulbs and dimmers.

It also does not happen all the time. As such it drives me bonkers and makes my house look possessed.

I live in FL in an "all electric" house.

Originally Posted by Mike Cudahy

OK, it's my own house,

We knew you would give up the information you were holding ... once we turned to water boarding ...

On of my EE buddies suggested some cross-talk between dimmers,

Can't quite figure out why he/she would say that, unless maybe the dimmers and lights are on a shared neutral (multi-wire) circuit ... but even then ... well, they be the EE, I'm not one o' them.

but I can't figure what changed to start the problem - I even changed the suspect bulbs and dimmers.

Change the dimmers to switches on one of the offending lights, see if the problem goes away. This is the opposite of what I suggested in a post above.

I see two choices on tracking this down:

1) As I suggested above in a previous post, remove all but one dimmer and replace with switches. Add one dimmer at a time after you feel that enough time has passed that the problem is still not there.

2) As I suggested in this post, remove one dimmer and replace with a switch. See if that solves the problem.

Both will work through the process of elimination of whatever is causing the problem. Once you have it narrowed down to one or two switches/dimmers, it would be in those circuits.

Method 1) is a sure fire way to eliminate dimmers as a cause.

Method 2) is less work if you find the offending dimmers/circuits before removing all dimmers.

I live in FL in an "all electric" house.

What part of Florida? Click on the User CP and update your location to include your city. Thanks.

Things to consider:
Most (if not all) photo cell lights (dawn to dusk) and motion sensor lights cannot be used with dimmers or CF's.

Are the dimmers electronic or mechanical? If old school mechanical dimmers, then you can rule out "cross-talk" theory. If electronic dimmers, then anything is possible (does the neighbor use their garage door remote a lot? ).

Process of elimination like Jerry is talking about is about the best bet.

They worked fine for a while, then they acted up - so here's what the flashing looks like;

http://www.ppfahome.org/temp/lamp.mov

this is a 10 Meg Quicktime video - the light seems to run normally - flash - then run normally - flash at a different rate - it's really crazy. I didn't touch a thing.

since the blinking or flikering fixtures are simple incandescent lamps, take a look inside the actual lamp sockets, sometimes you'll see the tiny rivet which holds the neutral wire connection to the lamp socket shell is slightly loose and is arching between the rivet and shell connection. You can change the socket or fixture at that point.

Now that's for a single fixture flickering, if your talking multiple fixtures flickering at the same time, it could be a bad connection at either the wiring to or from the switch or dimmer or even ahead of that like at the breaker or neutral connections in the panel. I traced my flickering lights to a bad connection at one side of the transformer connection at the power pole. The supporting evidence for that one was half of my house was flickering as was my neighbours house.

Originally Posted by Joe Klampfer

---I traced my flickering lights to a bad connection at one side of the transformer connection at the power pole.

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A Free Service Call to your Locale Utility company to check the connections on their side would take that item off your list as a possible cause.

Originally Posted by Billy Stephens

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A Free Service Call to your Locale Utility company to check the connections on their side would take that item off your list as a possible cause.

Sure... sounds easy enough but my first Hydro service tech opened up his underground connection pit by the street and said the problem was in my meterbase and left. I then asked my neighbor if he too was experiencing the same problem and called Hydro back. The 2nd service guy found the burnt connection at their transformer a 1/2 block away.