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- Air Quality & Ducts
- Home Performance
- Plumbing & Water
April 15, 2015
Outside AC unit not running? Perhaps the fan inside the furnace unit runs, but doesn’t blow cool air?
Here are a few of things you can do before calling an AC repair company.
Make sure the thermostat is set to COOL
A repair person will check this first, so you might as well, right?
Ensure that your thermostat is set to COOL and then set the temperature setting at least 5 degrees below the indoor temperature.
Look for a blown fuse or tripped circuit breaker
If there was a power surge, your air conditioner might have blown a fuse or tripped a circuit breaker.
Look for this problem in two places:
- Your main electrical panel — On old homes this is a ‘fuse box’ while newer homes have a circuit panel. If it’s a fuse box, look for a blown fuse (replace that thing!) On a circuit breaker, look for a tripped circuit and flip it to “off” and then back to “on”.
- At the shutoff box near the AC — Some models of air conditioners have a fuse at the shutoff box. Try replacing this fuse.
IMPORTANT NOTE: If one of these methods fixes the problem, but only temporarily—call an AC repair company. Your air conditioner may be pulling too much electricity, short circuiting or overheating (the later two are serious problems).
Related: Why Does My Furnace Keep Tripping the Circuit Breaker (Yes, we know it’s about furnaces. But much of the same information applies.)
Check the emergency or shut-off switch
Most air conditioners have a shut-off switch near the outside unit. It’s usually a metal box that’s hanging on your house. If someone has recently worked on the AC, they may have left it in the “off” position on accident.
Check the inside unit’s power switch
There’s usually a switch in your attic, closet, or crawl space near your furnace that can shut off power to your furnace and indoor blower.
Because the switch looks like a light switch, people often accidentally flip it to “off”. Setting it to “off” turns off the blower, causing the inside unit to freeze, which makes your entire AC system shut down.
So make sure this power switch is in the “on” position.
Look for problems with your condensate drain line
When your air conditioner works, it creates condensation, which is drained out of your home via a drain line.
If this drain line becomes clogged, it will trip a safety switch that shuts down your air conditioner. You can possibly unclog the drain line using a wet/dry vacuum to suck out the blockage
Some homeowners have a condensate drain pump, which pumps the water out of the home. So if the pump breaks, the same safety switch can get tripped.
Learn more in our article: How to Prevent Thousands of Dollars in Damage from a Clogged Condensate Drain Line
Try resetting the air conditioner
Some air conditioners have ‘reset’ switches near the outside unit. You can try pushing this button to see if it helps.
If your air conditioner doesn’t have a reset button, try this:
- Turn off your AC at the thermostat
- Wait 5 minutes
- Turn it back on again
Still having problems?