If you turn off your AC on your Nest and it doesn't turn off immediately, there are a few reasons this could be happening. Outdoor Conditions The most frequent cause is that the temperature outdoors is high, and your air conditioner is trying to maintain the indoor temperature to what you have set your thermostat. Try turning up your thermostat by 5-10 degrees and see if your AC then shuts off. Here is how to go about adjusting the AC on your Nest Thermostat: 1. Open the Nest app on your phone. 2. Tap on the "Thermostat." On the screen that opens, you will see the "Thermostat Circle." 3. Tap on it and then tap the "Up" or "Down" arrows to adjust the temperature. If you want to adjust the temperature of your Nest Thermostat using the device itself, all you need to do is turn the outer silver dial to the left or right to increase or decrease the temperature. The display on the screen will indicate the new temperature you have set. Safety Temperatures Another reason your AC may not be turning off is that Nest employs a unique feature called "Safety Temperatures." This application is designed to protect your home in the case of extreme external temperatures. So, although you may have turned off your Nest Thermostat, if the external conditions reach a particular temperature, Nest will enable "Safety Temperatures," to keep your AC on or your heating going to maintain a comfortable indoor environment. Here is how you disable this function in the Nest app: 1. Open the Nest app. 2. Locate the "Settings" app. (the gear icon.) 3. Tap on the "Equipment" option. 4. Choose "Safety Temperatures." 5. Slide both sliders to turn the settings off. Here is how you disable "Safety Temperatures" on the Nest device: 1. Press the display to call up the "Quick Menu." 2. Turn the outer dial to highlight the "Settings" option and tap on the screen to select it. 3. Select "Equipment." An "Equipment Detected" screen will appear. 4. Press "Continue." 5. Choose "Continue" again on the "Your System" display. 6. Select "Safety Temp." 7. Use the dial to select "Off." 8. Tap "Done" to exit. Now that you have disabled this feature, Nest will not automatically turn on your AC or heating systems.