How to Turn Off the Outside HVAC Unit Power

Warning: that there is a level of danger when dealing with anything electrical. If you do not feel comfortable with the steps below, contact a trained professional.

What's the AC Disconnect Box For?

The purpose of an AC disconnect is to break the flow of current in a circuit to stop the flow of power when installing or servicing any piece of electrical equipment. HVAC disconnects are usually located near the equipment so that the technician can easily see if the power is off as well as turn it off for servicing your unit.

Here is a common HVAC disconnect box. The cover just flips open with a hinge at the top. Below you'll see what it looks like when the cover is open.

Be careful in case there are any wasps in there!

Remove the Pullout Head

With the disconnect cover open, grip the pullout head and pull it straight out. It is designed to be put back into the disconnect box upside down, where it will not complete the circuit. Or you can just leave it someplace safe like on top of the disconnect box. When you are putting it back in, you'll see (look real closely) the words "OFF" and "ON" to the sides of the receptacle. If you put it in and see the word "OFF", then there is no power flowing to the unit. If you see "ON", then the circuit is completed, and power is being sent to the HVAC unit.

Make sure there is no debris in the disconnect box. Quite often critters or wasps can find a way in, especially if there are gaps around the box. Gently blow out any debris or use an old paint brush to sweep it all out.

Clean the Pullout Head

While you have the pullout head close to hand, take a look at the connectors. If they are corroded or dirty, now is a good time to run a piece of fine grit sandpaper across each of the contacts and wipe it down with alcohol to ensure a strong electrical connection. In this picture, you see it's been sanded down a little bit to get the surface nice and shiny.

With the pull out head removed (or reinserted upside down so that the word "OFF" is visible), the power is now off to your HVAC unit, and you can safely work on the unit.

When you have completed your repairs or maintenance, to restore power to the unit, simply insert the pull out head back into the slot from where it came. It should go in with just a little bit of effort as the contacts go back into the housing. If it slides in too easy, check to see if it's been installed upside down.

Close the door to the disconnect box.

If it's a warm day and the AC was running prior to your maintenance work, the unit should start back up. If not, turn down the thermostat so that the AC kicks back on. Listen out for any odd noises.

Should you be experiencing any issues, reach out to the pros at Dallas Heating and Air Conditioning.