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Home Electrical Troubleshooting FAQs

The categories listed below are all geared to solving malfunctions and miswirings in your electrical system, not code or design concerns (for which, see Basic wiring). For an overview of my troubleshooting information and tips, go to The Circuit Detective Home page. For FAQs on other topics go to Basic knowledge or Switching, bulbs, testing.


Circuit breaker questions
GFI-GFCI questions
Odd lighting behavior
Finding source of short circuit
Finding a ground-fault
Outages
Finding a loose connection
Overloads
Shocks
High utility bill

Circuit breaker questions

Does a circuit breaker go bad or get weak?
It doesn't start tripping at a lower level than it should, unless a loose connection/contact in/under/at it is making heat that throws it off. There are cases where the handle of the breaker mechanically will not reset, but it is more common that failure to reset is from a short that is retripping it immediately or is from the person not knowing the right procedure for resetting. Of all electrical problems, breakers get a lot of suspicion, and only a fraction of it is deserved.
How can I tell if a circuit breaker is bad?
(In general see Test). You can replace it or move its wire temporarily to another breaker. If this doesn't improve things, the old breaker is fine; look for another cause than the breaker. For instance, an Open.

GFI-GFCI questions

What is a GFI for?
A GFI receptacle or a GFI breaker is to prevent fatal shocks at likely locations -- where people operating faulty tools or appliances can easily become a good path to ground, completing an unintended circuit. See my GFCI article.
Is there a difference between a GFI and a GFCI?
GFI stands for "ground-fault interrupter". GFCI stands for "ground-fault circuit interrupter". They are the same thing. I prefer "GFI" because the word "circuit" is ambiguous or superfluous in most contexts.
What does the little light on a GFCI outlet mean?
Many newer GFCIs do have an LED light, but they mean different things on different brands. So I have not tried to memorize the light colors and their meanings. But if a GFCI normally shows no light but does now, or if it normally shows a light and now doesn't, then this is probably to tell you that the GFCI is tripped. In addition, the presence of a lit light also tells you that the GFCI has power available to it, so that its inability to run things is from being tripped and not from lacking power to its box.
How does a GFI work?
By "work" here you mean how does it know to trip off. (A GFI receptacle/outlet also "works" as any outlet does: by running what you plug into it). A GFI trips off (stopping power at itself and at any normal outlets wired downstream from it) by comparing how much current is flowing on its hot versus its neutral wires; it trips if these are different by even a small fraction of one amp, which might be the result of someone being shocked (giving current an alternate path than just between hot and neutral). But, unfortunately, many other conditions are able to trip these devices than someone being shocked.
Why won't my GFI reset?
There are several possibilities. It may be responding to a ground-fault happening somewhere downstream (at regular outlets that are now dead, for instance). It could be the GFI itself has no power reaching its electrical box because of a short or an open or another GFI that is tripped upstream from it. GFI receptacles made since 2002 will not let you reset them if power is not getting to their line terminals. See GFIs.
Does a GFI go bad, and how can I tell?
The main way a GFI truly goes bad is that it still runs things after you push the test button. In that case, it is not protecting anyone from fatal shock, at itself or at other outlets it was protecting. The idea that a GFI might be bad because it won't reset is almost always wrong. GFIs made since 2002 won't reset if they are not receiving good power in the first place. And a GFI receptacle made before 2002, whose reset stays in, can fail to run things for the same reason -- not receiving good power itself. In other cases a GFI "not resetting" is just retripping, for some kind of ground-fault; this is not a case of the "GFI going bad" either; it calls for correcting a fault condition downstream from the GFI. Only once or twice have I seen a GFI trip or fail to reset from a mechanical problem in it. See GFIs.
If my GFI (GFCI) won't reset, should I replace it?
You could, but it is much more common for a GFI receptacle to retrip (or to not reset) for other reasons than a bad GFI. Your new GFCI would probably not reset either. I wouldn't suspect the GFI itself till I had ruled out the more usual causes. Here they are. There could be a ground-fault happening at some "downstream" wire or receptacle or item plugged in. Your GFI that won't reset could have been installed incorrectly recently; since 2002 GFI receptacles have had a feature that won't let them reset if they are hooked up wrong or if power is not reaching them. Learn more about GFIs.

Odd lighting behavior

Where is the flickering of my lights coming from?
From a poor connection or contact somewhere along the circuit or even at a main wire outdoors or in the panel. Finding the problem-point isn't usually easy. See Flicker.
My lights dim down for a time or get extra bright; what's going on?
Some dimming when a copier, iron, or motor comes on is normal. Otherwise, a neutral wire -- usually the main one at the panel or outside from the power company -- could be having trouble. This would be confirmed if you also notice unusual brightening of other lights or of the same lights at other times. Repair is more likely to be a job for the power company than for an electrician or yourself. See Main open and Two Circuit.
I turn an appliance on and it makes lights that were dead come on; what's happening?
A main hot wire is having trouble at the panel or outside. The power company is often responsible, so call them first. Otherwise or later, an electrician. To understand what is going on see Weird electrical.

Finding source of short circuit

A breaker retrips when I reset it. If it is a short, where should I look?
If it is truly retripping, not having a rare mechanical problem, and you are attempting the reset correctly, then it is a short. On that circuit unplug everything and turn all simple switches off, and one end of any three-way switches the other way. If the short recurs upon resetting, see next question.
To find my short I turned off all the switches and unplugged everything of the circuit. Why is it still shorting?
The short is in a more permanent part of the wiring (in a box, receptacle, or wire). See Short. Have you made sure you know the extent of the circuit (outdoors, closets, attic, crawl space)?
I suspect that recent screws or nails hit a wire. Can I tell which screw?
If you are able (at the panel, for instance) to unconnect the neutral and ground wires and keep them isolated from anything grounded, then when the breaker is reset, it may not trip. If it does not trip, your ground and/or neutral wires will probably register hot, as will the theorized nail or screw and many appliances on the circuit! So put people out of the house before doing this! A non-contact voltage tester would then indicate pretty well which of all the screws is live. If you can touch its head with a neon tester (one probe in hand), it will confirm the culprit. Extracting it might leave the cable functional and safe, but you could bare the structure to be sure or to make a definite repair.

Finding a ground-fault

Since my GFI keeps tripping, where do I look for the ground-fault?
This will be similar to finding a short circuit (above) with the additional aspect that the fault to ground can come from the hot or from the neutral. See Ground-fault.
How can I find what is tripping the GFI if it only happens once in awhile?
On this question, I share your pain. I haven't done it much, but theoretically an ohmmeter might show a non-infinite resistance of over 30k ohms between ground and either hot or neutral, when you test (with power off) at the downstream (load) side or at any fully disconnected point downstream. This resistance won't have been enough to trip the GFCI but may be enough to track down the fault. Unfortunately we can sometimes get a similar reading across wires that are virtually separate. Also this idea won't help much if the fault is to the earth alone, not to the ground wire.

Outages

How can a circuit go out with no breaker or GFCI tripped?
In a word, by a connection being bad somewhere. The whole circuit would fail to work if a connection-point at the breaker or at the circuit's neutral in the panel became loose or deteriorated. More often these "opens" involve less than the entire circuit because a connection out on the circuit -- at an outlet box for instance -- has failed.
Some things are not working; how can I know where to look for the problem?
If you have checked bulbs and generator switches, and have reset any breakers and GFIs, you will probably need to look for an open (loose, corroded, broken) connection. Learn about Troubleshooting outages.
Some things will go out for awhile and later come back on (on their own); what is that?
That is a poor connection being poorer sometimes and better at other times. It may be generating some heat at the poor spot whenever it does run things. It will tend to progress toward staying out and never coming back on. See Comes and goes.
Why would a neutral wire read live?
When a neutral is not continuous back to the panel like it should be, the hotness of the hot wire still goes through anything that is ready to run (but won't) and shows up on the normally-neutral wire.

Finding a loose connection

I've narrowed my outage down to a loose hot or neutral somewhere; can I find the spot without tearing everything apart?
Maybe. For details on how to narrow the spot down see Finding your open.
I've checked, tightened, or replaced all my dead outlets and switches, and they're still dead. Now what?
Have you considered that the bad connection can be at a nearby working outlet or switch as easily as at a dead one? There may be odd places you haven't checked -- another room (downstairs?), a smoke alarm box or a doorbell transformer box (in a closet).

Overloads

How can I tell if I am overloading a circuit?
Most easily by letting the breaker trip and then recall what all was running that now is dead. If the breaker doesn't trip, you are not overloading. Are you "overloading" a receptacle, surge strip, or extension cord by the number of things you have plugged in? Not likely, although you should check the tag on the extension cord for the most watts you should have running on it. Even when these things are within their limits, any cord or receptacle can get hotter than it should because of a defect in or damage to it; if you notice extreme heat, replacement is a good idea.
The breaker often trips when I am using the vacuum (or hairdryer or iron); is that normal and what can I do?
It is almost normal, since the manufacturers of vacuums and hairdryers have increased the percentage of a circuit's capacity their appliances use. If it is too inconvenient to live with this problem, a new circuit to an outlet just for such a heavy user will do the trick.

Shocks

I get shocked when touching two things at once but not either alone; which one is bad?
Without a tester, the only way to tell is to touch a third or fourth thing from each, at some risk to your health! So I recommend a neon tester or a non-contact tester. See Testers and Shock.
We get shocked off faucets or pipes sometimes; what can we do?
The particular circuit responsible can be identified and the stray wire located. See Shock. Plus the grounding of those pipes should be checked and insured.

High utility bills

Why has my electric power bill been so high lately?
First, think of whether you have been using more; refer to Michael Bluejay's page on electric usage. You might also see if the power company is willing to check or replace their meter. If your water is heated electrically, a leaking hot water pipe would definitely explain a high bill. (There can also be a small increase in usage when a water heater's internal dip-tube, which sends cold water down to the bottom of the tank, is broken in the upper part of the tank.) Beyond that, I know of one instance in which a ground-fault to the metal frame of a building ran up the bill; the condition usually did not trip a breaker because the building frame was not grounded and the current leaking into the earth remained mostly less than the 20-amp setting of the breaker.


"Your site and your advice helped me locate an old outlet that was literally glowing and smoking when I found it. This is the best site I have ever seen anyone put up. I know you don't make much money from it and your generosity makes it even more remarkable." -Lawrence

© 2006-2013 Larry Dimock

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