An air conditioner that was running fine and then suddenly won't come on at all is frustrating, especially on a hot day. Often the cause is simple. Here's what to check, in order, before you call. If it's running but blowing warm, see why your AC is blowing warm air instead.
1. The thermostat
A blank screen is the most common cause of all: replace the batteries. Then make sure it's set to Cool and the set temperature is below the room. A smart thermostat may have lost its Wi-Fi or switched to a schedule or "away" setting.
2. The breakers
Most systems have two breakers in the electrical panel: one for the indoor unit and one for the outdoor unit. If one has tripped, you can reset it once. If it trips again, leave it off and call. A breaker that keeps tripping is protecting something.
3. The switch by the indoor unit
Many indoor units have a switch nearby that looks like a light switch. It's easy to turn off by accident when someone changes a filter or a bulb. Make sure it's on.
4. Water and the drain safety switch
When the condensate drain clogs, many systems have a safety switch that shuts cooling off so water doesn't overflow into the house. Look for water in the drain pan or around the indoor unit. If it's full, the drain needs clearing, and the system will usually start again once it's clear.
5. The filter and ice
A badly clogged filter can freeze the indoor coil, and some systems shut down when that happens. If you see ice on the copper lines or the coil, turn cooling off, set the fan to On to thaw it, and change the filter before trying again.
6. The outdoor unit
Check that nothing is blocking it and that its disconnect (a small box on the wall next to it) hasn't been pulled or switched off. If the unit hums or clicks but its fan doesn't spin, turn the system off and call: running it that way can damage the compressor.
When to call a technician
- A breaker trips again after one reset
- The outdoor unit hums or clicks but won't start
- You smell burning, or see scorch marks
- Ice or water comes back after you've cleared it
- Everything above checks out and it still won't run
Please don't open the electrical panels on the equipment. Call us at 805-965-6326 or send us a message, and let us know what you've already checked.
Related
- Air conditioning repair and installation
- Why is my AC blowing warm air?
- Repair or replace your air conditioner?
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