In the heat of the summer, turning your thermostat to air conditioning mode, only to find that warm air emerges from the vents, can be incredibly frustrating. You might figure that your air conditioner is done — kaput — but in reality, there are many possible explanations as to why an air conditioner won't turn on, and some of them are pretty easy to solve.
One possibility is that one or more of the wires leading to your air conditioner have become loose or are shorting out. This can occur if a rodent chews on the wires, which is not outside the realm of possibility since the condenser sits outside! The wires leading from your thermostat to the air conditioner can also come loose. Luckily, this is a rather easy problem for your air conditioning contractor to fix. They can reattach a loose wire, and in the worst-case scenario, they may have to run some new wires to the air conditioner.
Your air conditioner relies on a substance called refrigerant to cool off the air that it blows out. If the coil springs a leak, refrigerant may seep out. If enough seeps out, your air conditioner will no longer cool. If your air conditioner has been leaking recently, you may be able to diagnose a refrigerant leak by looking below the coil. Note any green or pink fluid; this is leaking refrigerant. Most refrigerant leaks can be repaired. Your AC contractor will weld or otherwise seal up the hole in the coil before adding new refrigerant to the system.
Note that refrigerant leak repairs are typically only recommended on AC units that are less than 10 years old. AC units that are older than this used a different refrigerant, called R22, which is no longer available. If you have an older AC unit with a refrigerant leak, installing a new air conditioner is your best choice.
Broken Fan Motor
If no air comes out of the vents at all — even cold air — then this could mean that you have a broken fan motor. There are numerous issues that can occur within a fan motor, just as with a car motor. The most common, however, are a loose bearing or a torn belt. Both of these issues are easy for an HVAC contractor to fix. They'll just remove and replace the damaged bearing or belt.
Typically, a fan motor will give you some noisy warning signs before it simply quits on you. If the motor was making banging, scratching, or squealing noises in the days leading up to failure, this is almost certainly what you're dealing with.
Your air conditioner has a filter to trap all of the dust and debris that blows through the system before it can reach the air conditioner itself. You're meant to change this filter every couple of months, but so many people forget to do this task. If the filter becomes completely clogged with dirt, the air conditioner won't be able to pass air through it. Attempting to blow air through the filter may cause the motor to overheat and the air conditioner to switch itself off. This is a safety feature to prevent fires.
You can try changing the filter and resetting the air conditioner to see if that helps. If the air conditioner still does not cool, you may need to call an AC repairs technician to make additional repairs for you.
If your air conditioner does not turn on, do not panic. In many cases, all you need are some simple repairs, and you'll be able to stay cool again.