Reasons for the AC to trip the circuit breaker range from the obvious “human error” issues with easy fixes to more complex matters for handy homeowners or licensed technicians to repair.
It’s a hot day and your house is uncomfortably warm. The thermostat is set to “cool” and the selected temperature is much lower than the displayed room temperature, but your AC unit is not working. A check of the circuit panel reveals that the breaker marked, “A/C” is tripped; it’s in the “off” position. Flipping it back to the “on” position has not solved the problem. Maybe the AC ran for a while and stopped again, or maybe the breaker tripped again immediately and won’t reset.
You might call a competent repair service and leave it to them to diagnose and fix the problem, but if you are a little bit handy – or even very handy – you might want to see if you can take care of it yourself before calling in the pros. Here are some things that can cause your AC circuit breaker to trip, and some things you might be able to do about it.
Non-Electrical Causes of the AC Tripping Circuit Breaker
Check these before calling for service.
1. Your Outside AC Unit Has a Cover On It
Oops!
At any big box store, your local hardware, or online, covers for the outside component of your AC system – the condenser – are available from as little as $10 to over $100, depending on the materials used to make them. Some people like to put a cover on their condenser even though they usually don’t really need it. But what happens if you forget to remove it before starting up your AC in the Spring? The unit will quickly overheat and the circuit breaker will trip. Simply remove the cover and allow the unit to cool down before trying it again.
2. A Very Dirty Furnace Filter
Here’s another one that just requires a gentle reminder.
Your central air conditioning system is part of the complete heating and cooling (HVAC) system in your home. It uses the same air ducts to circulate air throughout your house, and the same air filter through which all this cool (or warm) air flows. That means it is used much of the time, has a lot of air pass through it, and collects a lot of dust, dirt and pet hair (human hair, too).
If the filter is very dirty, it can cause the AC system to work so hard that it will trip the circuit breaker. Change your air filter at least every 3 months, and if you find it to be quite dirty at that time, you might want to check it monthly just to make sure it’s not too dirty.
3. A Dirty Condenser Coil
This is located in the outside AC unit, the cabinet that is usually in the back of your home or on a side where it is not easily seen. Inside this cabinet – around the sides – is the condenser coil. It looks something like a vehicle radiator, with many shiny aluminum “fins” and tiny openings for air to travel through. When the AC is running, air is drawn in through the sides of the cabinet, through the condenser, then out through the top by a fan. Dust, dirt, leaves, seeds and other outdoor debris can get trapped in the condenser coil and cause an “overload” when the system tries to start, tripping the circuit breaker.
To solve this problem, first make sure to disconnect the power to the outside AC unit. There is usually a disconnect plug very close to this unit which should be pulled out. It is also a good idea to turn the AC off inside the house. Remove the fan and grill from the top of the cabinet with the screws holding it in place and set the fan off to the side, being careful to not damage its connecting wires.
Rinse the condenser coil thoroughly with water, either with a nozzle on a spray setting, or just by squirting it from the hose with your finger. Do not use a pressure washer. Too much pressure can damage the delicate fins and keep the unit from circulating air efficiently. It is best to rinse from the inside out, so as to not push the offending debris deeper into the coil.
We’ve recommended the top tips and the Best Coil Cleaners in this Guide.
4. Too Little or Too Much Refrigerant
This isn’t one you can check, but it’s a possibility to discuss with an HVAC pro.
Every AC system uses a special liquid refrigerant which circulates through its components to make it work efficiently. The system is sealed, so it usually doesn’t require any additional refrigerant for life. If your AC has developed a leak, it will lose refrigerant, cause it to malfunction, and possibly trip the circuit breaker.
Normally, when a competent technician has fixed a leaking problem, everything should work as it is intended to.
However, if the technician somehow “overcharged” your system by putting too much refrigerant in, that can also result in a tripped AC circuit breaker. Always be sure to hire a well-respected and competent service technician if you need professional help with your AC.
Electrical Problems
Some of these are DIY opportunities if you are familiar with electrical systems and testing them.
1. Burned Out Condenser Fan Motor
This is the fan motor located at the top of the outside cabinet. If this motor burns out, it can definitely cause the AC circuit breaker to trip. One simple test that you might try to confirm that this is the problem is to gently spin the fan blade with a stick or long screwdriver. The fan blades are easily seen through the grill on top of the cabinet. If the fan turns very sluggishly or barely turns at all, the motor is most likely burned out.
Another, but more involved way to test the fan motor is to trace the wires from the fan motor to the electrical component panel. This panel will be located on the same side of the cabinet that the wires come in from your house. First, make sure to pull the disconnect plug near the outside unit. Remove the side panel and find the wires from the fan motor. Identify them by their colors. Remove them from the terminals and make sure they are not touching any metal or each other.
Now turn on the AC. If it doesn’t trip the breaker with the wires removed, the problem is with the fan motor. To confirm this, turn off the breaker again, replace the fan motor wires in the panel and turn the breaker back on. A burned out fan motor will cause the circuit breaker to trip again and it won’t reset. Contact a competent technician to replace it if you do not feel that you can do the job yourself.
2. Bad Wiring/Wire Shorted to Ground
This problem would most likely be in the outside cabinet. After first pulling the disconnect plug, a careful inspection of all wiring is what is needed to find the trouble. Check all wiring between the disconnect and the cabinet. Look for damaged areas – perhaps where wires run into the cabinet, though they are often in a conduit.
Remove the side panel where the wiring enters the cabinet; all the electrical stuff is there. Look for mouse nests, chewed or broken wires, especially those that lie against the metal cabinet. If a bad wire is found, cut and reconnect it with a butt connector and crimp pliers.
Another place to check is inside the box on the side of the compressor. The compressor is the “can-looking” part that is located on the bottom of the cabinet, and must be accessed by removing the fan and top grill. There are 3 wires inside the box on the side of the compressor. Check these wires for frayed areas, especially if they are lying against the side of the box.
A problem with one or more of these 3 wires can be fixed with a QwikLug™ repair kit that can be purchased at most big box stores or anywhere that sells AC supplies.
3. The Compressor Is Drawing Too Much Power On Start Up
Do the lights in your house dim whenever the AC starts. This could be the reason.
The compressor does a lot of work, and especially after several years, can begin to draw more electrical power due to wear. This is not too unusual and can often be at least temporarily fixed by installing a “hard start” kit. This can reduce the amperage draw on start up by up to 50%. If you’re handy with electrical components, you may be able to do this yourself. If not, be sure to hire a competent service technician.
4. The Compressor Is Shorted Out/Shorted to Ground
If your AC breaker keeps tripping, a shorted out compressor is another likely cause. If it is, installing a new compressor is the solution, but it is usually best to replace the entire condenser, the whole outside component of your central air system. Bad compressors usually only happen in older air conditioners, and it’s more cost effective to start with a completely new condenser unit than to try to put an expensive new compressor in an old system. According to our AC Repair Guide, compressor replacement cost is $1,250 to $2,500 based on the size and model of the condenser unit. That money is probably best spent on a new system if your current unit is no longer under warranty.
Pro Tip: Make sure your warranty stays in effect by having your AC serviced every year – and keeping the records!
Like roofing companies, car manufacturers and others, HVAC equipment companies are notorious for denying warranty claims. Most warranties state that the homeowner must have the system serviced by a pro every year or the warranty will be voided. So, look for an HVAC company with a good reputation and affordable service plans, and sign up for one. With a service plan, you’ll get discounts on the maintenance and possibly on repairs too. There’s more information in our HVAC Warranty Guide, the most comprehensive of its type.
To test to see if your compressor is bad, first pull the power disconnect near the outside cabinet. Remove the grill and fan from the top by taking out the screws that hold it in place and carefully set it to one side. On the bottom of the cabinet, you will see the compressor, while the aluminum condenser coils will be on the sides.
Near the bottom of the compressor will be a box where the wires come in. Remove the cover to this box, and you will find 3 wires. There are two ways to test for a bad compressor; with or without a multi-meter.
With a meter: Set the meter to “continuity” or ohms (Ω). Pull one wire off at a time and check the pin (not the wire) for continuity to the compressor case. They should all test “open” or OL. If any of the wires test otherwise, that pin is shorted to the casing, which is ground. This means the compressor is bad.
Without a meter: With all 3 wires removed and not touching each other or the case, turn on the circuit breaker in the house and reconnect the disconnect plug by the outside unit. At the thermostat, make sure that the AC is on and at a temperature low enough to call for cooling. If the circuit breaker does not trip, the problem is probably a grounded compressor.
To confirm this, turn off the AC again, pull the power disconnect plug and replace the 3 wires on the compressor. Replace the power disconnect plug and turn on the AC again. If it immediately trips the circuit breaker and it won’t reset, it is definitely a grounded compressor.
5. A Defective Contactor
The contactor is another electrical part in the outside AC unit. This can go bad, but it is quite unusual for it to happen. It must be tested with the power on, and is best done by a competent service technician. Does the unit sometimes buzz too? This is a clue that it is the contactor!
6. A Weak Circuit Breaker
If your AC breaker keeps tripping, it could be worn out. Sometimes – over time – circuit breakers can become “weak” and will trip, especially when a load is first placed on them. In one sense, this is a simple problem because it only requires replacing the breaker. However, it should not be considered lightly, because it requires the opening of the main power panel in the house and working with “live” power inside the panel.
If you have checked everything else and are still having trouble with the AC circuit breaker tripping, it’s best to contact a service technician to replace the breaker unless you are fully acquainted with working inside power panels.
Conclusion
When it comes to an AC circuit breaker tripping, one thing is sure: there is a definite reason for it to be happening. Just remember, central AC systems operate on 240 volts of electricity, so if you suspect any of the problems that appear to be electrical, be very careful unless you know what precautions to take. If not, be sure to contact a professional in your area who will be able to help you.
