How to Lock and Unlock Your Honeywell Pro Series Thermostat

Honeywell Home Pro series thermostats offer convenient lock and unlock features to safeguard your thermostat settings. This is particularly useful to prevent unintended changes, especially in households with curious children. You can choose between partial and full locks, depending on your preferences. In this guide, we’ll show you how to lock and unlock two popular models, the Honeywell T4 Pro and T6 Pro thermostats.

Locking and Unlocking the Honeywell T4 Pro Thermostat:

By default, the Honeywell T4 Pro thermostat is unlocked. Here’s how to lock it:

  1. Press the “Menu” button on your thermostat to access the menu.
  2. Use the “-” and “+” buttons to navigate through the menu options until you reach the “LOCK” option.
  3. Press the “Select” button to enter the lock settings. By selecting “PART,” you can partially lock the thermostat, allowing adjustments to the temperature only. Choosing “ON” will fully lock all settings.

To unlock the T4 Pro thermostat:

  1. Press the center button.
  2. Enter the PIN code. The default PIN is usually ‘1234’. Use the “-” and “+” keys to select each digit and press “Select” to confirm.

Please note that the default unlock passcode may vary for different models, so be sure to know your specific PIN before locking the thermostat.

Locking and Unlocking the Honeywell T6 Pro Thermostat:

To lock the Honeywell T6 Pro thermostat:

  1. Press the “Menu” button.
  2. Navigate to the “Screen Lock” option and tap “Select.”
  3. Choose between “Full Lock” or “Partial Lock.”

Before confirming the lock, you’ll see a 4-digit PIN on the screen. Make sure to note this down, as you’ll need it to unlock the thermostat.

To unlock a locked T6 Pro thermostat:

  1. Press the “Menu” button.
  2. Select the “Lock” option.
  3. Enter the 4-digit PIN to unlock the thermostat.

Unlocking Without a PIN Code:

If you forget your PIN code, you can unlock your Honeywell Home Pro thermostat using a workaround. Look for a 4-digit code beneath the serial number on the back of the thermostat. Add ‘1234’ to this number to calculate your unlock PIN. If this doesn’t work, you can also try using the first 4 digits of the serial number as your PIN, plus ‘1234’.


Locking and unlocking your Honeywell Home Pro series thermostat is a simple process that allows you to maintain control and security over your home’s climate settings. This feature offers peace of mind, ensuring that your thermostat remains tamper-proof and that your desired settings are maintained. By following the steps outlined in this guide, you can easily customize access to your thermostat and enjoy both comfort and energy efficiency with confidence.

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