What to check when your AC won't turn on

Why an AC won't turn on: start with power

When your AC won't turn on, the cause is often power or a control setting rather than a failed cooling part. A blank thermostat, a tripped breaker or a neighborhood outage can all look like a dead system. Each of those can be checked safely from the floor, without opening a panel.

Switch the system off and stop if you smell something burning or a breaker keeps tripping. Those are signs to leave the system off and call a licensed contractor.

What should you check at the thermostat first?

The thermostat is the control that tells the AC to run, so it is the first stop. A blank screen usually means dead batteries or no power reaching the thermostat. Put in fresh batteries if your model takes them, then see whether the screen wakes up.

If the screen is lit, look at the settings:

• The mode should say cool.
• The set temperature should be below the current room temperature.
• The fan should be on auto, since "on" runs the blower but does not start cooling.
• A hold or schedule setting should not be overriding what you just entered.

Some thermostats pause briefly before they start the system after a change. Give it a moment before you decide it is dead.

A thermostat that is lit and set correctly, with an AC that stays silent, points toward the breaker, the outdoor disconnect or the unit itself. For the bigger picture on repairs, see AC repair in Spanish Fork.

How do you check the breaker and the outdoor disconnect?

A tripped breaker is a common reason an AC goes quiet. The breaker sits in the main electrical panel, and the cooling circuit is often a double-wide switch. A tripped one usually rests in the middle position or toward off.

Here is the safe order:

1. Look at the cooling breaker in the panel without touching anything else.
2. If it is tripped, push it fully to off, then back to on, one time only.
3. Go outside and look at the disconnect box on the wall near the outdoor unit.
4. Check that the handle or pull-out block is seated and the box is closed.
5. Leave the box closed, and do not pull or replace anything inside it.

If the breaker holds and the AC starts, that may have been a one-time trip. If the breaker trips again, leave it off. A repeat trip means something is drawing too much current or shorting, and resetting it again can make that worse.

Electrical parts and wiring are contractor-only work. A licensed contractor checks the wiring, the capacitor and the contactor, and so on. A homeowner should not open the outdoor unit or the disconnect to look.

Is it a power outage or an AC fault?

Start by checking other things in the house. If lights, the microwave and the refrigerator are all off, the whole house has lost power, and the AC is not the problem. If everything else works and only the AC is dead, the thermostat, breaker or equipment is the likelier cause.

The city's website names Spanish Fork Power & Light as the provider of electric service to homes and businesses in Spanish Fork. That is the place to look for outage information if the whole house is dark.

After power returns, give the system time to restart. Many units hold off briefly after an outage to protect the compressor. If the AC then starts and stops over and over, the guide on why an AC keeps starting and stopping covers that pattern.

Weather makes a dead AC easy to notice. The weather station near Spanish Fork averages 60 days a year with a high of 90°F or more, and the average June to August daily high there is 89.8°F. A cooling system that won't start is hard to ignore on those days.

When should you stop and leave it off?

Some signs mean the next step is a licensed contractor. Switch the AC off at the thermostat, and leave the breaker off, if you notice any of these:

• A burning or hot electrical smell near the unit or the vents.
• A breaker that trips again after one reset.
• A loud hum or buzz from the outdoor unit with no fan spinning.
• Scorch marks, melted plastic or a breaker panel that feels hot.

Two safety rules apply to any heating or cooling trouble. If you smell gas, leave the house, then call the gas utility from outside. If a carbon monoxide alarm sounds, get everyone out and call emergency services.

Refrigerant, sealed components and electrical parts are not homeowner work. A licensed contractor tests the electrical supply, the control board and the parts that start the compressor and fan. The contractor then confirms what needs repair.

Next step if the AC still won't start

If the thermostat is set right, the breaker has been reset one time and the power is on, the fault is likely inside the system. At that point the fix belongs to a licensed contractor.

The main page on how AC repair works in Spanish Fork explains the phone line. Where a contractor is available, the line connects the call to a licensed, insured contractor.