Go to your home thermostat and set it to the "Off" position. You must do this before resetting the main switch.
Locate the grey power box mounted near the outside air conditioning unit. According to Carrier HVAC, the box is typically 8 inches wide and 16 inches high. Note that the color and exact location of the box may vary.
Open the box and locate the main power switch. Move the power switch to the off position. Leave it in the off position for at least a few minutes.
Switch the power switch back to the on position. Wait at least 12 hours before using the air conditioning unit.