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“My AC won’t turn off. What should I do?”

While most people think of air conditioner breakdowns—situations where their AC units won’t turn on—as the most likely air conditioning problem, the above question is actually one that HVAC technicians hear pretty frequently, as well. In normal circumstances, your AC unit will switch on and off many times throughout a day—especially a particularly hot summer day. Even in mild spring or summer weather, your AC unit will usually run 2-3 times per hour, for about 10-15 minutes each. This cycling allows the AC unit to keep your home or business temperature at or close to the set thermostat temperature, as well as to combat humidity. If your air conditioning unit is turning on much more frequently than usual, though, or if the AC unit actually won’t turn off, those are problems worth a call to your HVAC technician.


AC Won’t Turn Off: What’s the Problem?

There could be a few different explanations for why your AC unit no longer seems to be going through the normal on-off cycle. If the unit is turning on repeatedly, running for a few minutes each time, and then abruptly turning off again, then the problem likely has to do with air conditioner size. An oversized AC unit will typically behave this way. In contrast, an undersized unit will have to run more often (and for longer) to achieve the thermostat-set temperature. The only AC fix is to replace the unit with a properly-sized unit. To avoid these types of outcomes, it’s never a bad idea to consult an HVAC expert before you buy an AC unit, to make sure it is appropriately sized for your space.


If your AC truly will not turn off, though—even when you shut off your thermostat—then there is a different kind of problem at work. The most common explanation for this type of issue is a stuck compressor contactor. The compressor contactor, essentially, is the mechanism that notifies your AC unit that it’s time to turn on. When the thermostat is on—or when it detects that the temperature in a space needs to be cooled—it sends a 24-volt current to the compressor contactor. The contactor then closes, which delivers power to the compressor and the condenser fan motor and tells the air conditioning unit to run. When the thermostat decides that the correct temperature has been reached, it switches off that 24-volt current, causing the compressor contactor to close and cutting off power to the compressor and condenser.


The problem with this system is that, as electricity is bridging the compressor contactor, it creates an arc of electricity that generates heat. Over time, this heat can cause the contacts on the compressor contactor to melt, effectively welding them together. Thus, the compressor contactor becomes stuck in a closed position, leaving the contactor unable to separate and maintaining a flow of power to the AC compressor and condenser. In this situation, the AC unit will continue to operate—and continue to cool your home—even if the thermostat is shut off.


If you believe you are experiencing this problem, call your HVAC technician for an air conditioner repair. The good news is that swapping out a welded compressor contactor is neither a time-consuming repair nor a particularly expensive one. Calling your local Santa Rosa HVAC expert to check on the issue as soon as it arises will mean that you don’t have to deal with an out-of-control AC unit. If the temperature in your home is becoming uncomfortable due to the excess air conditioning, a temporary fix is to shut off the breaker on your circuit board that corresponds to the AC unit. This step will at least stop power to the unit, which will give you some relief from unwanted air conditioning. It’s not a permanent fix, but it will make the wait for your HVAC contractor a bit easier.


Other Potential Causes

While the most common causes of an AC unit that won’t turn off are the two we’ve discussed so far—a stuck compressor contactor or an improperly sized unit—there could be other issues behind your current home cooling woes. Sometimes, there could be something wrong with your thermostat itself (or at least with the wiring or installation) that is causing miscommunication between the thermostat and your AC unit. Problems with clogged air filters, dirty condensers, dirty evaporator coils, low refrigerant levels may also be the culprits. These issues can make it difficult for an AC unit to cool a space properly, thus making the thermostat temperature more difficult to reach. These problems can typically be avoided by taking care of your AC unit with regular maintenance.


Call for an Air Conditioning Repair in Santa Rosa

Regardless of what is causing your air conditioning unit to run indefinitely, calling in a trusted HVAC expert is likely the answer. Someone who knows their way around an HVAC system will be able to diagnose whatever is behind your problem and recommend a fix. So, if you find yourself in an “AC won’t turn off” crisis, don’t fret! This problem is more common than you think, and the solution is typically just one phone call away.


Sources: https://reddihvac.com/blog/cooling/why-wont-my-ac-fan-turn-off