The Aquasource shower faucet is a single handle model faucet with a small adjusting knob on the front of the cartridge. This valve is also called the stop-limit or scald guard, and it prevents burning and scalding due to very high shower water temperatures. If your hot water is not hot enough or too hot, you can adjust the faucet's temperature output by rotating this knob slightly. The fast fix only takes about 10 minutes.
Find the screw on the bottom of the faucet handle and unscrew it with an allen wrench.
Take the handle off the faucet base by pulling it away from the shower stem. If the handle sticks in place, attach a handle puller to the handle and turn the post to slowly slide the handle back and off the faucet's stem.
Remove the handle adapter, if there is one on your model, with a screwdriver.
Turn the limit stop knob, the small knob on the end of the faucet's cartridge to the left or right to increase or decrease the temperature of the water.
Turn the end of the faucet's stem clockwise with a pair of pliers to turn the water on as hot as it goes. Allow the water to run for at least a minute. Test the temperature of the water or insert a thermometer in the water and read the temperature. Turn the water off by turning the stem counterclockwise. Adjust the knob as needed. Generally speaking, 105 degrees Fahrenheit is a suitable temperature for a shower.