To troubleshoot the reason your AC unit won’t turn on, start by making sure its circuit hasn’t tripped. Next, make sure your thermostat is functioning properly. If it is, then go outside to check the condensate pump and the electrical connections. Finally, try testing the unit’s dual run capacitor.
Once you’ve figured out why your AC unit won’t turn on, fixing it can often be surprisingly easy. We’ll walk you through both the troubleshooting steps and what to do to fix the problem you find. You could get your AC unit started back up right now. Start by heading to your circuit breaker.
1. Trip the circuit breaker
Your central electrical panel splits electricity from your main distribution line out to every electrical fixture throughout your home. This could include both your thermostat (if it’s connected instead of battery-operated) and your AC unit itself. Circuit breakers trip to protect your fixtures when they sense a surge of dangerous amounts of electricity. Tripped circuit breakers cut all electricity off to the fixture they’re protecting until you reset them.
Tripped circuit breakers are surprisingly common. You may only notice that a circuit breaker tripped when you notice the fixture won’t turn on. Find your main electrical service panel and look for tripped breakers. The tripped breaker will be shifted down to the “OFF” position rather than the “ON” position, and may also be indicated by a red warning label. Simply flip the circuit breaker back on and see if your AC unit starts back up.
2. Test the thermostat
If your thermostat isn’t functioning correctly, then it may not send the proper cooling instructions to your AC unit. Even if the AC unit is perfectly functional, it will never turn on because it doesn’t know that you’re telling it to! Malfunctioning thermostats are usually easy to spot. If the display won’t turn on, it doesn’t respond to inputs, or it immediately loses programming, then something’s wrong. Try replacing the batteries or, again, tripping a circuit breaker.
If nothing seems wrong with your thermostat, there is one relatively simple way to test it. First, turn off the power to your thermostat (THIS IS IMPORTANT). You’ll need a screwdriver. Take down your thermostat and open up the access compartment in the back. Find the red and green wires, unscrew them from their terminals, and manually wrap them together. Then, let go of the wiring and flip the breaker back on. If the AC unit starts, then you need to replace the thermostat.
3. Clear the Drain Line
While you have the access panel open, locate your unit’s condensation pump. This pump removes moisture that builds up on the unit’s condensation tray by pumping it through the drain line. This drain line harmlessly deposits the condensation outside of the unit. If the drain line becomes clogged, however, then the pump won’t be able to remove condensate. Instead, it will build up inside the AC unit until the unit’s safety features stop it from activating.
Unclogging the drain pump is relatively easy. First, turn off the power to the AC. Locate the tray, pump, and drain line. If you have a hand vac, suction out any excess moisture in the tray. Then, disconnect the drain line and use the hand vac to suction out clogs inside it. If you don’t have a hand vac, use water or compressed air. After reassembling the components, reintroduce a little moisture to the tray to make sure everything works properly.
4. Replace the Dual Run Capacitor
Dual Run (or Dual Round) Capacitor malfunctions are among the most common AC problems. These capacitors sit inside the AC unit’s access panel split power to supply the fan and compressor at once. When they stop working, then the fan and compressor won’t be able to begin the cooling process. Finding, testing, and even replacing the Dual Run Capacitor in your AC unit is easy. Here’s how to do it step by step:
What you’ll need: a screwdriver or nut driver (depending on your unit), pliers, and a duster of some kind.
- Turn off both the power to your AC unit and your thermostat.
- Open your access panel using the screwdriver or nut driver. Don’t lose the screws!
- Locate the Dual Run Capacitor. It’s usually located on the upper component box within the access panel. Dual Run Capacitors are cylindrical, bolted to a holder, and connected to the electrical supply via three differently-colored wires.
NOTE: The Dual Run Capacitor may be located next to another capacitor. In that case, look for the capacitor labeled with “COM,” “FAN,” and “HERM” inputs. - Dust off the upper component box with your duster. Check the wires for signs of damage while you’re at it.
- Unscrew the Dual Run Capacitor from its mount and remove it.
- Check the labeling on the side of the capacitor to find the capacitor’s micro-farad rating (which will be labeled “uf”). This is the rating you’ll need to know to buy your replacement capacitor. Take a picture, write it down, or take the actual capacitor with you when you buy a replacement.
- Buy your replacement capacitor either online or at your local hardware store. Make sure you get one with the same micro-farad rating.
NOTE: Your new Dual Run Capacitor may be smaller than your current one. That’s not necessarily a mistake. You may need to adjust the capacitor mount when reinstalling. - User the pliers to disconnect the capacitor from the three wires connecting it to the power supply. Make sure you remember which wire goes where (consider taking a picture with your phone).
- Connect each wire to the new capacitor.
- Re-mount the new capacitor back in the upper component box. You may need to adjust the mount or re-mount the capacitor yourself.
- Restart your power and adjust your thermostat to test the new capacitor. It may take 10-15 minutes for your AC unit to restart.
If you’ve tried each of these common troubleshooting steps and you still can’t get your AC unit to turn on, don’t panic! These steps haven’t exhausted all the possible quick fixes; just the ones you should try yourself.
Whether you’ve exhausted your troubleshooting options or not, you can always call Mike Diamond for back up. Our professional electricians offer reliable, licensed help that will solve your problem and cool your home down again fast. AC is especially important during summers when we can’t leave home, so don’t cook yourself any more–if your AC won’t start, call Mike Diamond now!
