Light Switch Makes Popping Sound

[John Ross]

This is a switch in a bathroom that turns on a light on the ceiling and also a fan (actually, the fan is separate from the light and has a plug that goes into a receptacle next to the fan--1960 squirrel cage type). So the single switch actualy controls the light and an outlet for the fan.

For a long time there was an intermittent problem where when you flipped the switch, it would make a popping sound. I recently had the switch replaced and asked the electrician if there was any sign of wires damaged or burned. He said no and replaced the switch.

Well, it is not as loud as it had been at it's worse, but I can still occassionally hear a slight pop when turning it on. Any ideas on what would cause this type of thing?

-- John

[RBM]

When the contacts in the switch touch, the load of the lights and motor cause an arc inside the switch which can sometimes be audible. You might want to replace it with a heavier or better grade of switch

[DerbyDad03]

[DerbyDad03]

As long as you need to repair this situation, I suggest you install a separate fan switch, preferably a timer or humidistat style.

Right now when you leave the bathroom you are either leaving the light on to ensure the fan clears the moisture, or you are turning off the fan before the moisture is cleared. The former wastes electricity, the latter can result in mold and peeling paint. (This assumes showers/ baths are taken in the bathroom)

In any event, you're wasting electricity every time you turn on the light (and therefore the fan) even if you're just combing your hair or brushing your teeth, assuming you have both.

[Tony Hwang]

Hi, If you don't like the sound, replace it with a hospital grade switch which won't arc.

[John Ross]

So you are saying it is normal under this kind of condition and not a safety issue? Therefore, putting in "heavier grade" switch is just optional if it bothers me?

-- John

[RBM]

Every time you get that pop, it's burning away a little more of the contacts inside the switch. At some point it'll stop working properly and need to be replaced. A better grade of switch, like spec grade, or a heavier rated switch such as a 20 amp, will have more substantial contacts, and will make a more positive connection, so it will be less likely to make a pop, and will last longer

[frantic]

I can hear the sirens of the fire truck rushing to your house right now. You need a qualified electrician. Call one NOW. This is an EMERGENCY. Or shut off the power to your entire house until one arrives. You might see flames shooting out of that switch any minute. Kill the power NOW.

[RickH]

It's back EMF (electro-motive-force) from the motor starting up. This actually causes the switch contacts to "bounce" making the noise and an internal spark. With squirrel motors the current circulates around the coil and the rotor (squirrel) inside the coil "follows" that circulating current. For there to be zero back EMF the rotor would have to be in perfect speed synch with the coil current flow, but it never is, especially at start up time when it is standing still. Cheap paddle ceiling fans can also show this symptom, but the more expensive fans have a capacitor circuit to absorb some of the back emf, the real cheap ceiling fans dont so they make a noise too I've found.