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Why is My Honeywell Thermostat Not Turning on the A/C?

Last Updated Oct 26, 2021
honeywell t9 thermostat
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Smart homes are becoming the norm, and many people are trying to save on energy costs by installing smart thermostats. The problem is, no matter how good they are, you’re dealing with sophisticated software, and unfortunately, there are occasional hiccups.

There are a few reasons your Honeywell Thermostat may fail to turn on your A/C when it’s time: Neglected air filters, wiring problems, low battery, or the need to be reset are the most common issues.

Honeywell thermostats are designed with quality features, hardware, and—in the case of their smart variations—software as well. However, they’re like any other thermostat in that they are vulnerable to certain things. Also, like any other thermostat, the troubleshooting is often the same. Below are some troubleshooting steps you can take for each common issue:

Identifying if the Honeywell Thermostat’s Wiring is the Issue

Unless you are an electrician by trade or have a wealth of knowledge and experience in handling wires tied to alternating current, you should call a professional to come by and check the integrity of your wiring system.

To determine if it’s the wiring or the thermostat that’s the problem, remove the Honeywell thermostat from the wall. Disconnect the red and white wires from their current position and touch them together.

If your air conditioning turns on, you don’t have a wiring problem. If it doesn’t, then you’re going to have to call an HVAC crew out.

Change the Batteries in the Honeywell Thermostat

Regardless of the system you are using, the batteries will always be in the back of the device—assuming that your model has batteries at all.

Any time you decide to remove the Honeywell thermostat from the wall panel, always be sure to first turn the device off and then cut the power at the circuit breaker. Once you’ve removed the device, replace the batteries and remount it, remembering to return power from the circuit breaker. Often, a fresh battery is all that’s needed.

Reset the Honeywell Thermostat

Since we’re using the term, “Honeywell Thermostat,” that means that you may be sitting there with a 9000 series while someone else reading this article has a 7000 series. We’ll fill you in on how most reset to factory settings to avoid any confusion.

Honeywell 9000 Series

To reset the Honeywell 9000 series:

  1. Select the Menu button followed by Preferences.
  2. You’ll have to scroll down a little bit to find Restore To Factory Default. Once you do, select it and follow that up with Yes.
  3. Once you hit yes, the thermostat will reset itself back to its “out-of-the-box” settings.

Honeywell 8000 Series

The 8000 series has a pretty simple reset procedure:

  1. Start by pressing System on the screen and then hold down the center “blank” button for five seconds.
  2. When prompted, select Reset to Factory Settings.

Honeywell 7000 Series

The 7000 series involves a little more legwork than most of the others:

  1. Power down the thermostat, cut the power to it from the circuit breaker, and remove the thermostat from its installation plate on the wall.
  2. There should be two triple-A batteries in the back of the thermostat. Remove them and wait five minutes.
  3. Replace the batteries, reinstall the Honeywell thermostat, and flip the breaker back on. By the time it powers up, it should be factory reset.

Honeywell 6000 Series

To reset a thermostat from the Honeywell 6000 series:

  1. Press and hold the Fan button and—while still holding the fan button—press and hold the Up button arrow.
  2. After five seconds, release them and press the button on the bottom, left-hand side until the display says “39.”
  3. Press the Down button until 0 is highlighted on the display, followed by Done.

Honeywell 4000 Series

For a Honeywell 4000 series thermostat:

  1. Press and hold the button that says Program.
  2. Insert a paperclip into the tiny hole at the bottom of the device while holding the button. The system will factory reset.

Miscellaneous Troubleshooting

If your A/C still doesn’t turn on after the above troubleshooting steps, try the following:

  • You’d be surprised at how often an A/C system won’t kick on when the air filters have been neglected for a long period. Be sure to replace them regularly. Smart thermostats, such as the Ecobee3 Lite, will inform you when it is time to replace them.
  • Check the copper cooling line running from your house to your outside unit. If it is frosted over, your evaporator coils are probably messed up. This is something that often happens when the air filters are neglected.
  • Lastly, contact Honeywell Customer Support if all else fails. They will be able to provide you with detailed troubleshooting tips for your specific Honeywell thermostat.

Final Thoughts

Unless you’re an HVAC or electrician professional, going beyond the tips listed above will probably lead to contacting someone to come have a look at your system. The above tips are the most common problems for a Honeywell, as well as all the other thermostats out there.

If it looks like something you can fix, don’t hesitate to contact customer support or HVAC. Sure, HVAC is expensive, but a long hot summer or a cold winter will be the least of your problems.

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