Electrical short from water?

[Monkey Wrench]

Several weeks ago the overhead lights would blink off then on once a day. That was when we started having rain at night but not during the day so I wasn't worried about it. Then the first day when it started raining day and night for four days the overhead lights in three rooms and all the wall plugs in one of those rooms went dead.

I got in the attic and checked to see if any water was getting in but everything looked dry and good. I resisted the temptation to stick my hand into the blown insulation to see if it was wet with an electrical current flowing through it.

When the rain slacked off I checked the outdoor breakers, cleaned out a wasp nest, got stung twice but everything looked good.

When I put the voltage meter on with all the light switches turned off and nothing plugged into the outlets it showed 75 volts but as soon as a switch was turned on or something was plugged in it went to zero volts.

I took down all the overhead lights, checked them out and put new light switches on, cut and stripped new wire connections. When I turned on the light switch the light came on for half a second then went out and stayed out until a few minutes ago. They just started working. It hasn't rained for two days. All of these are on the same breaker. Would an electrical short caused by water do this or would it be more likely there's a loose connection somewhere?

Thanks for any advice Monkey Wrench

[hallerb]

yeah water can do that.

get some good flashlights, turnm off main breaker for home and explore looking for wet insulation.

with main breaker off you can get shocked

[Toller]

I had a very similar problem. Turned out that one of my exterior outlets had corroded and had an intermittent bad connection. Replaced it and everything is fine. I expect you have something similar. You just have to go at it one component at time and see where the problem is. You have an open circuit, not a short circuit. A short circuit would trip the breaker, which you said it didn't.

[peter]

Water has relatively high resistance. They are not likely to cause a short circuit severe enough to dim lights. A short severe enough to dim lights would probably trip a circuit breaker. Your symtoms sound like an intermittent open circuit.

Check for loose connection on this circuit in all junction boxes starting from main panel to the lights. If there are receptacles between the panel and the lights, plug a lamp in it. It would help you narrow down the problem area (binary search).

[RBM]

Sounds like a loose wire somewhere in the circuit

[Jeff Wisnia]

I'd like to hear your explanation of how water can do that without popping the breaker.

The only thing I could imagine is water swelling of some piece of wood with wiring stapled to it enough to cause a pull on a "loose disconnection" and open the circuit, but that's a very long shot I think.

I think you meant ON.

Jeff