Ecobee Not Turning On AC? (Possible Causes & Fixes)

It’s a major drag when your AC stops working, but that doesn’t always mean it’s time to replace it. Sometimes, the fix is really quite simple.

As with any mechanical device, an Ecobee thermostat can sometimes fail to do its job. You may find, on occasion, that your Ecobee thermostat no longer controls your air conditioner. But what could cause your Ecobee to stop turning on the air?

The most common reason an Ecobee won’t turn on your air conditioner is due to excessive water build-up in the drain pan. If it’s not the HVAC system, there could be a wiring problem with your Ecobee either at the thermostat or the HVAC control board. You may also need to reconfigure your Ecobee equipment or change the threshold settings.

The location of these parts depends on the make and model of your HVAC system. Drains pans and evaporator coils may be on the top or bottom of the furnace or air handler. The pan may even be on side of the unit or on the ground. The condensate line is usually made of white PVC pipe and is on the side of the furnace.

If your HVAC system is in the attic, it most likely has two drain pans. The main one is under the evaporator coil. The secondary or “backup” pan is under the air handler.

The easiest way to empty the drain pan is to use a wet/dry shop vac. Simply vacuum up the water and dispose of it. Then, clean any mold or mildew build-up inside of the pan. If you don’t feel comfortable emptying the drain pan yourself, enlist the help of an HVAC specialist.

You may also need to flush the drain pipe. The access point for the pipe should be a T-shaped vent tee. First, remove the cap. Then, for the best cleaning results, pour in ¼ cup of distilled white vinegar. Let it sit for 30 minutes before flushing the pipe with water. Do this once a month to avoid a full drain pan.

Note: if you don’t have distilled white vinegar, you can also use peroxide or hot water with a dash of dish soap.

Make sure the wiring is consistent between the thermostat and the HVAC control board. The Y1 terminal at your Ecobee should be connected to the Y terminal at the control board.

For those with a PEK, the Y1 wire at your Ecobee should be connected to the Y terminal at the PEK. From the other end of your PEK, the Y wire should be going to the Y terminal on the HVAC control board. Also, check the security of any splice points in the wires.

There are two wires coming from the outdoor compressor that should also be connected. This wire bundle is separate from the thermostat wire bundle. The compressor wires should be connected to the Y and C terminals in the control board. The compressor will not engage if these wires are not secure.

You can check your equipment configuration in the Ecobee app or on the thermostat itself. Note: if you have a PEK, your equipment configuration steps will be different.

Go to Main Menu > Settings > Installation Settings > Equipment > Wiring.

If you have separate heating and cooling systems, you should see RC and RH highlighted. Otherwise, RC should be highlighted. In either scenario, Y1 should be highlighted as well.

If something is not correctly highlighted, you need to reconfigure your equipment. Do this by going to Main Menu > Settings > Installation Settings > Equipment > Reconfigure Equipment.

The first screen will ask how many R wires you have connected. Select the one that is appropriate for your type of HVAC system. Next, you’ll see all of the wires detected by Ecobee. If Y1 is not highlighted, select the “No” option on the bottom left because this wiring is not correct.

You will then be prompted to modify the selected wires. Manually add the Y1 terminal so that it’s highlighted. Click “Next” and follow the rest of the on-screen prompts to finish the reconfiguration process.

Finally, your compressor thresholds for the outdoor temperature and cycle time might need to be adjusted. Go to Main Menu > Settings > Installation Settings > Thresholds.

Your compressor won’t run if the outdoor temperature is below the minimum value on this threshold setting. You can verify the outdoor temperature by checking the main screen of your thermostat.

Your compressor turns off between cycles and this amount of time has a default setting of 5 minutes. When Ecobee completes a cooling cycle, it turns off for 5 minutes and will turn back on again once that time is up. You can set the minimum cycle time off to however long you want.

Do you still have questions about your Ecobee’s cooling functions? You’ve come to the right place. Below are some questions other people asked about the cooling functions of Ecobee thermostats.

To enable this feature, go to Main Menu > Settings > Installation Settings > Thresholds > Auto Heat/Cool and then choose “Enable.”

You may have your fan setting to “On” instead of “Auto,” which means it will continuously run until you manually turn it off. When the fan is set to “Auto,” it will automatically run when it senses the temperature needs adjustment. You might also need to adjust the threshold for minimum fan runtime so it doesn’t run for such a long period of time.

Ecobee recommends a minimum fan runtime that’s between 5 and 20 minutes. This means the fan will run for 5 minutes every hour or whatever number you set it to. The length of time you run the fan depends on your environment. But it’s not recommended to continuously run the fan.

An Ecobee calibrates to get an accurate temperature reading of your house. While it’s calibrating, you are unable to use the HVAC system. Once calibration is completed, the HVAC system should activate again.

It’s frustrating when your Ecobee thermostat doesn’t turn on the AC. That’s pretty much its main job! Thankfully, though, this issue is usually caused by a full drain pan, which is very preventable.

First, check that the HVAC system is running properly. If you notice puddles of water near the unit or water damage around the drain pan or pipe, your problem is most likely excessive water build-up in the unit.

After emptying and cleaning the drain pan and pipe, you can troubleshoot your Ecobee if you’re still noticing issues. Check that all wiring is secure. And then, reconfigure the equipment and adjust threshold settings as needed.