I have a digital multimeter, but I'm having the worst of luck testing whether a circuit breaker I have is working properly, or if it is a different issue with the wiring in the circuit box. I first used this video as an instruction, but failed to realize that although the video doesn't say it, it is important to make a distinction between the common lead and positive lead. I almost fried my multimeter. Not wanting to try that again, I figured the best approach would be to turn off the main power, remove the circuit, and test the resistance instead. I can't seem to get a reading at all on the breaker no matter what I do. Can someone provide better instructions?

I know it is a problem with a single circuit (either the breaker or the wiring for that circuit) because all of the other circuits and breakers are functioning properly. This happened after I plugged a light into an outlet, and thought I saw a small spark. Nothing on that circuit is working now.


It sounds like your circuit breaker is tripped. Often they don't look much different between tripped and one of the full on or off states. To reset these types of breakers, you usually need to manually flip them all the way to off, then back to on. You can't go directly from tripped back to off.

If you remove the breaker completely, then it should look just like a switch electrically. There should be a short accross its terminals when on, and open when off. You should be able to test this easily with a ohmmeter.

In the panel, you can look for the AC voltage between the output of the breaker and neutral. That should be your line voltage when the breaker is on, and zero when off. As long as your voltmeter is set on the appropriate voltage range for your wiring, nothing should blow up. The meter is a open connection as far as the house wiring is concerned. You have to work at it to blow something up, like put the meter on amps scale or something.

Testing whether the breaker trips when it's supposed to is a whole other issue, but you don't seem to be asking about that.

  • \$\begingroup\$ "As long as your voltmeter is set on the appropriate voltage range for your wiring, nothing should blow up." What about reversing the positive and negative leads when testing? The video shows the positive lead on the lead into the breaker, and the negative lead touching the box. If you put the negative on the lead into the breaker and the positive lead on the box, then I suspect that would also cause an unfavorable reaction like I got? \$\endgroup\$
    – user5636
    Sep 5 '11 at 23:08
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    \$\begingroup\$ A multimeter has no required "polarity" of leads to work properly. The leads are usually coloured simply to enable you to interpret the relative polarity of the source you are measuring. Reversing the "positive" and "negative" leads will not cause any problems if your multimeter is set to measure voltage. It will simply reverse the polarity of the reading displayed if set to DC, and if set to AC should read the same either way. Of course your multimeter may be faulty. Try it with a battery and put the black probe on the positive end and red on negative - it should display a negative voltage. \$\endgroup\$
    – Oli Glaser
    Sep 6 '11 at 1:12
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    \$\begingroup\$ @Brian - have a look at this page on multimeters. \$\endgroup\$
    – Oli Glaser
    Sep 6 '11 at 1:18
  • \$\begingroup\$ @Oli: You seem to be assuming digital multimeters. Analog ones do care about polarity in some cases because the needle goes only one way. However, this case is about AC voltage, so none of this matters for either kind of meter. \$\endgroup\$ Sep 6 '11 at 11:09
  • \$\begingroup\$ @Olin - yes, I was talking about digital multimeters as the OP mentions a digital multimeter. You're right though, I should have mentioned Analog ones too, which need a bit more care taken with - even when set up the right way if too much voltage is applied whilst on the wrong range it can damage the delicate needle IIRC (been a long time since I used one) \$\endgroup\$
    – Oli Glaser
    Sep 6 '11 at 12:54

A circuit panel is not a good place to learn electricity. Unless you are experienced and know what to do, leave this job for an electrician. If the whole circuit is out as you say, it is possible the breaker is faulty. You may think you are safe by shutting down the main breaker, however the utility power is still hot within the panel.

I will ask the obvious, did you unplug the lamp that originally tripped the circuit breaker then reset the tripped breaker to see if the rest of the circuit came back on? There are several different types of panel circuit breakers, among them are GFCI, AFCI, and a standard type time inverse current breaker. The first two will have a white wire going to the neutral bus, as well as the black "Hot" wire that all of those will have. GFCI & AFCI also have test buttons on them.

For instance If the breaker was an AFCI (Arc Fault Circuit Interrupter) type, it should have tripped when the plug sparked at the outlet. This is a protection device against faulty appliances as well as faulty wiring. If it is a GFCI (ground fault circuit interrupter) that will detect if current is imbalanced in the circuit, possibly returning to ground, where it will trip the breaker (hopefully) before you can be shocked.

If you think the breaker is defective, I strongly suggest you have someone who is qualified replace it.


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