Reset your temperature limiter if your shower valve fails to produce water that is hot enough for your needs. Remove your shower faucet knob according to the manufacturer's instructions, and set aside.
Use your pliers to grip and open the faucet valve completely, and allow the water to flow.
Use a thermometer to check the temperature of the water. Hold your thermometer under the water for a period of about 3 to 4 minutes for an accurate reading.
Insert the end of your Allen key into the set screw located on the left side of the faucet valve. The set screw determines how far the valve can turn, and therefore how much hot water is allowed to flow through the faucet.
Turn the screw counterclockwise to increase the amount of hot water allowed. Turn the screw clockwise to allow less hot water.
Open the faucet valve completely, and use your thermometer to test the water temperature again. If the water is still not at a satisfactory temperature, move on to step 5.
Use your flat head screwdriver and wrench to remove the O-ring and stop collar if an adjustment which is larger than the set screw will allow is required. Pry the O-ring and stop collar away from the valve, and use your pliers to remove it completely.
Turn the threaded valve stem which was formerly covered by the stop collar. Use your wrench to twist the stem to the right to increase the flow of hot water and to the left to decrease it.
Replace the stop collar and O-ring on the valve so it remains in the original position, leaning against the solid metal tab at the top. Tap it into place with your hammer.
This will permit the faucet valve to release more hot water and raise the temperature of the water accordingly. Test the water temperature again to ensure it is satisfactory.
Replace your shower faucet knob.