How to test if an electrical outlet is working correctly
A malfunctioning outlet is typically a quick fix, something you need not hire a professional electrician for if you follow the proper steps. As with any electrical job, safety comes first. 120 volts will do a lot of damage to careless hands, so always wear protective gear when working near a live outlet (e.g. rubber gloves, safety glasses, etc.).
A lot of homeowners have a tendency to assume the worse when something goes wrong, particularly if they lack experience in the home improvement department. The first thing to check is the circuit breakers; high energy loads are quite frequent and the breaker box is in place to prevent extensive damage to electrical wiring when a problem occurs.
Breaker, GFCI or Wiring: Check all Three
Something as simple as flipping the breaker switch back to the “On” position is all it takes to get the outlet working again. If a circuit fuse is in question and you cannot locate the source, proceed to cycle every breaker off and on. Contact a local electrician if the problem persists, as this may indicate a potential ground fault or short circuit issue. Faulty or damaged wiring is likely the culprit, a job intended for an expert.
All modern outlets feature GFCI technology, which stands for ground fault circuit interrupter; these devices are used to terminate the power source quickly when a ground fault occurs. Take a look at the outlet. Push the little red button in the center and see what happens. When there is more current going out than coming in, the GFCI will engage. If you have ever had multiple electrical devices running at the same time that were not linked to a power strip, chances are this has happened.
Determine if the problem exists in isolation. Is the outlet in question the only one not working? Test the voltage of nearby outlets and see if they still function. Since GFCI outlets will trip when current leaks are detected, you can save some trouble by ensuring all of them are reset (common areas to check are bathrooms, kitchens, garages and basements). If the GFCI continues to malfunction, it may need to be replaced.
Lastly, loose wiring at the breaker or the outlet could be the problem. Unscrew the outlet and check the condition of the leads. At this point you may find a one of the wires has been removed from the connector, simply twist it back together and this should fix the issue. It would not hurt to install a new wire connect while you have the device open, too.