Based on a similar issue, to change the fan relay speed on your s40 thermostat, you would need to adjust the wire connections on the blower relay. specifically, you would take the black wire and put it on the #2 terminal on the blower relay, replacing the blue wire. please note that this process involves handling electrical components, so it's important to ensure the power is turned off before making any changes to avoid any risk of electric shock. if you're not comfortable with this process, i would recommend reaching out to a professional or lennox technical support for further assistance. also, if you're looking to adjust the fan speed through the thermostat settings, you can follow these steps: 1. in the upper left corner of the main screen, press the menu button. 2. on the menu screen, select the fan option. 3. select the fan mode from the available options and then press the home button to save the choice and return to the main screen. if you encounter any issues during this process, please don't hesitate to reach out to lennox technical support for further assistance.
For more information or a visual representation of steps please reference our user guide here
