I have one circuit in my home that is defying all explanations as to its behavior. This circuit is on a bedroom with ensuite bathroom and the lights (an other items) attached to the circuit will blink unexplainedly. Some times so much so you would think that the power was going go off completely.

I had an electrician in and he replaced all the breakers in the main panel and for one week it seemed to have solved the problem but not so.

I have no clue what is happening and the electrician is equally baffled. Sometimes I wonder if the problem is weather related since it happens more often in damp/rainy weather.

If anyone has any ideas about what might be the cause please send me email.

You say one circuit and the lights (and other items) blink unexplainedly? What kind of items other than lights blink? You "would think the power was going off completely"? Does that mean that it is happening in other parts of the house, other than the bedroom/bathroom. I and several other enthusiasts on these boards will be more than happy to try to help solve your problem, but I don't think by emailing you our "solutions". We may have many questions we need to ask you in order to come up with a theory or two and we wouldn't necssarily have the sme suggestions to offer, but we would like to know what each of the others have already mentioned. If the problem is indeed confined to the one branch circuit which includes both bedroom and bathroom, that would seem to suggest that the house is probably an older one. The vintage could mean that there is a loose and intermittent connection or splice in one of the junction boxes, because of a wire nut or terminal that is loose and introduces a high resistance. This type of problem would more than likely cause the light(s) to dim or vary in intensity rather tha the definite on/off type of blinking. All I can say about an electrician replacing ALL of the breakers in the main distribution panel, is that you need to change electricians. You DID say, only one circuit was behaving erratically, didn't you?
You don't say what vintage house we are dealing with, armored cable, non-metallic sheathed cable, knob and tube, EMT, etc. If high humidity, rainy weather seems to cause it, it could be intermittent leakage to ground, ground faults sufficient to cause momentary blinking of lights but too short of duration or magnitude to trip the circuit breaker supposed to protect that branch circuit. Very old Romex cable has an outer braid which tends to "wick" moisture. One other possible source of your trouble I can think of might be an air conditioner or other circuit that draws heavy current, which whenever it starts causes a considerable voltage drop in other parts of the house. Even a hair dryer plugged into a bathroom receptable is not sbove suspicion. Outside of an actual visit to your house to personally observe and conduct tests of my own, I'm afraid that's about all I can say about your proble. Maybe Donaldeklerios, or someone else will think of some other possibiliites. And welcome to the 'pool.

Thank you for the help.

The home is appproximately 25 year old so I would expect that the wiring is more or less up to date. Other than that I don't know what type of wiring was used. The blinking problem is confined to the one circuit in the house. The lights do, as you say, blink or vary in intensity rather than on/off blinking. There aren't any large power hogs running in the house. The a/c season has not yet started. Right now the only things on that circuit is a floor fan, a radio, a TV and two overhead lights (one with ceiling fan) which should not even cause a flicker.

I agree with Frank. It needs somebody independent to run tests on this circuit
using a Multimeter
Reading into what you say I think the root cause of the fault will be in a high place because you state that it happens in damp wet conditions ....so you have steam rising to the ceiling and rain coming down what is above the bath room? a flat roof? or a ventilation hole? even a suspended ceiling(supported by metal brackets)a small drop of water dripping onto the cable if damaged can cause weird faults Multimeters resistance will rise if there is any ingress,but report OK if it's dry (One of the times technology fails you )
I'd look visually for any semi exposed cable joint or made up terminal block with a bare wire (even exposed strands of wire!) Turn the Power off before doing this! or B) Inspect the entire run from circuit box to at least the first appliance that you know has one of these moods check there are no nails/staples
that have pierced the cable and that the area around it is wet/dampish Check also there are no wet/damp Ground cable points ( Only cure is to reposition them in a drier position)
I've worked on several cars with electrical Problems similar to this and It often turns out to be a wet/corroded /loose or (fallen off) ground connector/s

This message has been edited. Last edited by: bedstor,

One or two further thoughts or hunches based on what we now know. There is a radio, TV, and 2 overhead lights, one with ceiling fan. That light with the ceiling fan probably vents to the outside and is the most likely suspect for moisture getting to the wiring, as Bedstor suggested. I would suggest opening that up, and inspect the connections and any evidence of moisture. You don't mention whether or not the fan, TV, or radio are intermittently operating when the lights flicker? If they are, I would go back to the branch circuit breaker, identify the wires, black to the cct. breaker, white to the neutral bus bar, and bare copper (or green) to the ground bus. All of those connections should be inspected to see if they show corrosion, burning, or loose connection. Of, course the main breaker should be open when you are doing this. If in doubt, get someone else to do it!!