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When Your Electricity or HVAC Stops Working: What to Check Before Calling an Electrician

By Constance Obi · Culture & Recreation Writer

Start with the simplest fixes before you call for service

Most electrical and heating or cooling problems that seem urgent can be narrowed down or even solved by checking a few things yourself first. A tripped breaker, a clogged filter, or a thermostat set to the wrong mode costs nothing to investigate and takes minutes. Knowing what you've already tried also saves the electrician or HVAC technician time on the job, which can lower your bill.

This guide walks you through the most common issues and what to look for. If none of these steps work, you'll have real information to give the professional you call—and you'll know whether the problem is urgent or can wait for a regular appointment.

Key Takeaways

  • Check your electrical panel for a tripped breaker before assuming you need an electrician; flip the breaker all the way off, then back on.
  • Reset a tripped GFCI outlet (the kind with test and reset buttons) by pressing the reset button; if it trips again immediately, stop using that outlet and call for service.
  • A clogged air filter is the most common reason an air conditioner or furnace stops working, and replacing it takes five minutes and costs under ten dollars.
  • Check that your thermostat is set to the right mode (heat, cool, or auto) and that the temperature setting is actually calling for heating or cooling.
  • Write down exactly what is and isn't working, when it started, and what you've already tried—this information helps a technician diagnose the problem faster.

Electrical problems: where to look first

The electrical panel is usually in a basement, garage, or utility closet. Open the door and look for a switch that is in the middle position or flipped the opposite direction from the others. That's your tripped breaker. Flip it all the way to the off position, wait a few seconds, then flip it back on. If the breaker trips again immediately when you turn something on, do not keep resetting it—that means there's a short or overload that needs professional attention.

If you have outlets that aren't working in one room or area, look for a GFCI outlet—it has two buttons labeled "test" and "reset" in the middle of the face. Press the reset button. GFCI outlets are designed to cut power if they sense a problem, and resetting them often restores power to the outlets downstream from them. If the GFCI trips again within seconds of resetting, unplug everything from that outlet and the ones it controls, then try resetting once more. If it still trips, stop using that outlet and call an electrician.

Check whether the outlet itself is damaged—scorch marks, a burning smell, or a loose plug that won't stay in are all signs to stop using it. Unplug everything and call for service. Do not try to repair an outlet yourself.

HVAC problems: the filter and the thermostat

Before you call about heating or cooling that isn't working, locate your furnace or air handler (usually in a basement, attic, or utility closet) and look for the air filter. It's a flat, accordion-like panel, usually white or blue, that slides into a slot. If it looks dark, clogged with dust, or hasn't been changed in more than three months, replace it. Filters cost between five and fifteen dollars at any hardware store, and a clogged filter is the single most common reason a system stops working or runs poorly.

Next, check your thermostat. Make sure it's set to the right mode: "heat" if you want warmth, "cool" if you want air conditioning, or "auto" if you want the system to switch between them. Then check that the temperature setting is actually calling for what you want—if it's 72 degrees in your house and your thermostat is set to 70 in cooling mode, the system won't run because it's already cooler than the setting.

If your thermostat has a battery, replace it with a fresh one. A low battery can cause the thermostat to stop communicating with the furnace or air conditioner, even if the display still looks normal.

What to check on your outdoor air conditioning unit

Walk around to your outdoor AC condenser—the large metal box outside your house. Look for leaves, branches, or debris blocking the fins (the thin metal slats on the sides). Gently clear away anything you can reach by hand, but do not pressure-wash the unit or try to straighten bent fins yourself. Blocked airflow is a common reason an AC system runs but doesn't cool well.

Check whether the unit is running at all. You should hear a fan and feel air moving out of it when the system is on. If the outdoor unit is completely silent and the indoor part is running, the problem is likely electrical or mechanical and needs a technician.

If you see ice on the outdoor unit in winter, or if the system is running but producing warm air instead of cold, turn it off and call for service. Running an AC system that's frozen or low on refrigerant can damage the compressor.

Documenting what's happening before you call

Write down the exact symptoms: Is the power completely off, or is the system running but not heating or cooling? When did it start? Did it happen after a storm, after you changed the thermostat, or without any obvious trigger? Have you replaced the filter recently, or can't remember when you last did?

Note what you've already tried—resetting the breaker, replacing the filter, checking the thermostat mode. If you heard any sounds before it stopped (a pop, a buzzing, a grinding noise), write that down too. This information helps a technician understand the problem before they arrive and can mean the difference between a quick fix and a longer, more expensive visit.

If the problem is intermittent—the power cuts out and comes back, or the heating works sometimes but not others—describe the pattern. Does it happen at a certain time of day, after the system runs for a while, or when you use other appliances?

When to call right away versus when to wait

Call an electrician or HVAC technician immediately if you see scorch marks or smell burning near an outlet, breaker, or furnace; if a breaker keeps tripping no matter how many times you reset it; if your AC condenser is frozen solid; or if your furnace is making a grinding or squealing noise. These are signs of damage or a serious malfunction that can get worse if the system keeps running.

You can usually schedule a regular appointment if the system isn't working but there's no smell, noise, or visible damage; if you've replaced the filter and reset the thermostat and nothing changed; or if the problem is intermittent and not affecting your comfort right now. Many electricians and HVAC companies offer same-day or next-day appointments for non-emergency calls, especially during mild weather.

If you're without heat in winter or without air conditioning in summer and you've checked everything on this list, call for emergency service. Most areas have 24-hour HVAC services for situations where you need heat or cooling restored quickly.

Frequently Asked Questions

What does it mean if my breaker keeps tripping?

A breaker that trips once and then stays on is usually fine—something caused a temporary overload. A breaker that trips repeatedly, especially when you turn on a specific appliance or use a certain outlet, means there's a short circuit or overload that needs professional repair. Stop using that circuit and call an electrician.

How often should I replace my furnace or AC filter?

Most filters need replacement every one to three months, depending on the type and whether you have pets or allergies. Check your filter monthly by holding it up to a light—if you can't see light through it, replace it. A clogged filter makes your system work harder and can cause it to overheat and shut down.

Can I reset my thermostat myself?

Yes. Most thermostats have a reset button or a switch you can flip. Check your thermostat's manual or look for a small reset button on the device itself. Resetting clears any error codes and can fix communication problems between the thermostat and your heating or cooling system.

What should I do if my outdoor AC unit is making a loud noise?

Turn off the system and call an HVAC technician. Loud noises—grinding, squealing, or rattling—usually mean a fan blade is loose, a bearing is failing, or something is stuck inside the unit. Running the system with a noise like this can cause more damage.

Is it safe to use an outlet that keeps tripping the GFCI?

No. A GFCI that trips repeatedly is detecting a ground fault or moisture problem. Unplug everything from that outlet, stop using it, and call an electrician. Using it anyway risks electrical shock or fire.