Adjusting the shower temperature control valve can save you from an occasional burn if your elbow should push the single lever up by accident and the hot water showers on you instead. Because of the risk of scalding and energy that is wasted because water is kept at such a high temperature, it's a good idea to adjust the shower temperature control valve.
Uncover the Control Valve
Take a screwdriver and get underneath the handle cover and pop it loose. A valve hidden underneath the cover will immediately get your full attention. The valve will have a collar and two nubs. One nub will be positioned in the 12 o’clock state. Using the pliers, pull out nub and move in a clockwise direction and then placed back.
How far you move the nub from the original position will decide the maximum angle of rotation the handle is allowed to move. A handle that rotates minimally will be kept from going into its all hot water position. You might need to play with the nubs in order to get the angle of rotation, hence, the temperature of the water, you prefer.
If you run into more serious problems when you remove the handle, like rust or other degradation, you might want to consider replacing the valve entirely.