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Short Circuit but fuse did not blow?

Posted by Rikidoo (My Page) on
Mon, May 14, 12 at 17:51

I made the mistake of moving a light box without turning off the power. I believe the wire touched a screw and caused a short circuit. Everything on that circuit stopped working (a few ceiling lights and electrical outlets). When checking the fuse box, none of them has blown.

I have taken out the light box where the short circuit happened, it was connected to only one other light box, not in a loop. This didn't solve my problem.

Any suggestion on how to proceed to fix this would be very much appreciated.

Thank you!


Follow-Up Postings:

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RE: Short Circuit but fuse did not blow?

How did you test the fuses? Is there another fuse or circuit breaker panel?


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RE: Short Circuit but fuse did not blow?

I replaced the fuses on the affected circuit with new ones and it made no difference (replaced them on the fuse box).


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RE: fuse did not blow?

Plug fuses sometimes require tightening with considerably more torque than one imagines.


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RE: Short Circuit but fuse did not blow?

The sudden surge of a dead short can also cause a poor connection somewhere in the circuit to become an open connection. Specifically, I'd look at the receptacles and switches in the circuit and replace any back-stab devices found (they are notoriously unreliable), while also looking for loose connections and anything that 'looks wrong'.


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RE: Short Circuit but fuse did not blow?

It appears that you assumed that the new fuses were good. They almost always are so, but not absolutely always. At this point, it is necessary to examine everything in the most minute detail. Test all the fuses. Test all the voltages at each circuit in the panel.


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RE: Short Circuit but fuse did not blow?

It sounds like a weak spot in the wiring failed before the fuse.

It is now likely the open that is preventing operation of the portions of the circuit.


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RE: Short Circuit but fuse did not blow?

Umm...I'm not sure we still know that "none of the fuses were blown." If the short that caused the problem still exists, just replacing the fuse with another is going to result in an instantly blown fuse. Sometimes it's not possible to tell by looking in those little windows that the link is blown either.


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RE: Short Circuit but fuse did not blow?

Time to screw in a light bulb?


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RE: Short Circuit but fuse did not blow?

Thanks all for your replies. I don't think the fuse is the problem. Since my panel is not very well labeled, I've tested new fuses by switching all of them back and forth a few times. Everything was still working except the circuit where I did the short.

I'm thinking that I must now have an open circuit as some of you have suggested, but still couldn't find where it's opened. I don't think I have any backstab devices.

I suppose that I need to buy the gagdet that tells me if there's current and test every outlet and swtich on the affected circuit.

Otherwise, I'm thinking I should probably change my fuse box to a breaker panel.


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RE: Short Circuit but fuse did not blow?

I'm thinking that I must now have an open circuit as some of you have suggested, but still couldn't find where it's opened.

What have you done to try to find it?

Otherwise, I'm thinking I should probably change my fuse box to a breaker panel.

You do realize that won't solve the problem, right? But I guess if you are hiring an electrician to switch out the panel, he can easily find the problem with your circuit.


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RE: Short Circuit but fuse did not blow?

Fox and hound time (electronic signal tracer transmitter and receiver set).

An electronic signal generator (the 'fox') is attached to the lines at the panel, then a tracer (the 'hound') is used to follow the lines until the signal is lost.


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RE: Short Circuit but fuse did not blow?

What brand do you recommend brickeyee?
I was thinking of buying a set for fun but the Greenleee 1000 is super expensive.

so far I've gotten by tracing using an old fluke pro3000 tone tester kit. But that works when circuit is off not on - but has helped me trace a lot of wires.

I would love to have a good tester that works on a live circuit.


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RE: Short Circuit but fuse did not blow?

Ideal has some less expensive models.

The more expensive ones are often more rugged, sensitive, and have a sensitivity adjustment that makes them easier to use.

If the it senses on multiple breakers you dial back until it only indicates on one, then switch the breaker off and see if the unit stops sensing anything afte3r turning back to the highest setting.

Then use a meter to check the circuit before touching anything (NOT a 'non-contact' sensor).


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