Need Electrical Help: Light switch keeps tripping breaker?

Question

I have several lights and receptacles on one circuit. One switch controls 2 tandem fluorescent light fixtures in one room and throws the breaker when it's turned on. None of the other switches or receptacles on this circuit causes a tripped fuse. These are not new.....they've been working fine for a long time, then one day one fixture went out and the other still worked. Then while the second was on (this was about a month later), it popped and tripped the fuse and continues to when switched on (trips immediately).

I don't want to call in an electrician if I just need to replace the fixtures or balasts, but I don't want to try replacing them if it's a wiring/short problem (it's old wiring, so the insulation could have worn over the years causing contact, but I can't see any evidence......I won't try playing electrician anymore unless it's something simple). Any thoughts on what's causing this or how to correct or at least test for it? Thanks.

Answer 1

More than likely the problem is in the fixture that went out first. It could also be a problem with the switch itself or possibly damage to the wires from the switch to the lights.

With the breaker off, open the fixtures and inspect them for obvious damage/burns. If you don't see any damage, disconnect the feed (with the breaker OFF) and make the bare ends safe by putting the connectors back on the wires (the feed will come to one light and then a black & a white wire will connect to the second light). With the feed DISCONNECTED from the light and the switch OFF, turn the breaker ON making sure you stand clear of the breaker as it may pop instantly. If you have fuses take the same precaution (doesn't hurt to wear a glove - and DON'T look at the breaker as you turn it on!). Now with the breaker on turn the light switch on. Did the breaker trip? If not, then the problem is with one of the fixtures. Since the fixtures are old, I would replace both of them (a new 4' fixture isn't more then 20 bucks). At the same time you are replacing the fixtures, buy a NEW switch. Since you were tripping the breaker when you turned on the switch, you were causing a dead short at the switch. A dead short WILL damage the switch, it may still work, but replace it anyway.

If it does trip, I would replace the switch first. Now perform the above test with the lights disconnected.

If the breaker still trips after a new switch has been installed the problem is with the wiring. Have you screwed or nailed anything into the walls recently? You may have damaged the wire in doing so. In which case you need to rewire the light from the switch to the light. Rewire and buy a NEW switch again.

Best answer?

Cheers.

Answer 2

It's pretty obvious that it is the last fluorescent light fixture that is causing the problem. It is likely a short, but finding it might be time consuming, unless you can remove the fixture. If the fixture is removed, there should be no tripping. Then test the fixture with a simple continuity tester to find the short.

Make sure you are careful taking the fixture wires out of the wire nuts if you have not shut off the fuse to the whole circuit. You can also examine the wires in the ceiling to see if there are bare spots that might touch.

You may want to look for dampness that might also be causing shorts.

Answer 3

If the failed light has not yet been corrected then this needs to happen first before you can tell if it is the problem or if there is a different problem somewhere else in the circut.

If the breaker was fine with this load in the past then it's not an issue with the number of things on the circut. And if this is the only thing that causes this breaker to pop then it's not that the breaker itself is bad.

That kind of leaves a short in the bad light fixture which replacing the ballast or starter or other internal parts may in fact correct.

The other think you might want to consider before fixing the bad fixture is just disconnect it and put wire nuts over the ends just long enough to reset the breaker and turn on the light switch.

If the breaker blows with the light disconnected then there is a short in the wiring somewhere back in the line. If the breaker doesn't blow, then it is the bad fixture that needs repaired.

Answer 4

Two possibilities:

1. Breaker is going bad (especially if it is an old breaker). Pick one up at Home Depot or Lowe's (they're cheap). Make sure the new one is the same configuration as the old one.

2. It is possible that the circuit wiring has become worn so that the insulation is getting thin in spots, and causing intermittent "shorts" against something else. This happened to me, and it was a circuit that hadn't changed in years. I discovered that a wire was shorting out to a metal junction box, tripping the breaker. It wasn't visibly apparent, but I moved the wires around in the junction box and re-installed the wire nut, and the problem cleared up.

Answer 5

It sounds like your switch is grounding itself. You have a wire touching or something. Turn the switch on letting it throw the breaker. As long as there is no juice now at the switch, pull it out from the wall, check all the wiring. Your switch itself could be bad now so have another switch ready to change as long as the breaker is off. If you have 2 switches that work the lights make sure you get a 3 way switch. It's very easy to change. Just follow how you take the old one apart. # ways, red & black are hot so they will connect on the hot screws.

Answer 6

It definitely sounds like a short or loose wire somewhere. Obviously you're not terrified of electrical work, so check at both the light switch and the fixture if a wire connection has come loose. The other thing that's coming to my mind is water... Is there any chance there is water or even condensation involved here? I doubt that the fixture or ballast is the root of the problem here. Good luck!

Answer 7

Do you have a power tester? I would suggest getting one before you go any further. You need to determine which of the wires that were in place before you began connecting them together was the HOT or power wire; the one bringing power from the circuit breaker to the light. Remember that electricity flows. From what I can tell, in this case, you have power coming to the wall/ceiling box, then to the light fixture, and simultaneously to the switch. That's not correct. The circuit should only become complete when the wall switch is flipped. Even though you have black and white wires, it does not necessarily mean that they all have to be connected to each other. It can get confusing sometimes, but black isn't always the "power" wire and white is always the "neutral" wire. From the top: If there were 3 different wires coming into the box and you didn't have a wall switch before, then one set of wires is supplying the power/neutral and the other two are continuing on to another box somewhere else. Disconnect the power supply at the breaker. Remove the wires from your light fixture and the switch. Take the cap off the black wires and place the black wire coming into the box from the switch with them. Tighten the cap on all 4 wires. Connect the black wire coming into the light switch box to the "power" terminal on the switch. Connect the white wire coming into the light switch box to the "neutral" terminal on the switch. Connect the white wire coming from the switch into the fixture box to the BLACK wire leading to the fixture. Finally, connect the white wire coming from the light fixture to the other white wires. The ground wire should be connnected to the light fixture and continued on to the light switch box. In this instance, the power comes into the ceiling box, continues to the switch, then passes through the fixture. The white wire coming from the switch into the fixture box is actually the wire providing "power" to the fixture.

Answer 8

You can do it shut the breaker off to that receptacle box and remove the switch that is faulty go to home depot and buy a replacement and install in the same manner you took it out. It really is a simple small task. also on any of the wires that the insulation has come of use electrical tape.

Answer 9

The tip-off is the fixture that stopped working, that you left unresolved. All you had to do was disconnect the power to the ballast. Or, change the obviously bad ballast. But you left it cook, until something internal shorted. Then it was a big mystery why the breaker suddenly tripped. And still you could have disconnected the power to the ballast. But a dead fixture didn't seem to be causing any problems.

All I can say is be glad you have circuit breakers.

Answer 10

master elect. here. a bad ballast could easily trip the bkr. unhook each fixture and see it the bkr still trips.