When installing trim kit for mixet, temperature handle rotates freely and makes it impossible to correctly set water temperature.

Delta single handle Tub & Shower faucet temperature control adjustment.

Step 1 - Remove handle to gain access to rotational limit stop. Once handle is off there ia a plastic limit stop disc. Remember where it is to start with. Metal handles require a 1/8" allen wrench to remove handle. Plastic handles require removal of cap to access screw to remove with phillip's head screw driver.

Step-2- To adjust the temperature of the water coming out of the valve, pull the disc back to a position where it is possible to remove the Rotational Limit Stop and readjust the teeth to desired position to acheive temperature. Once moved reinsert it into place to test water

Step-3- Clock wise will decrease the temperature and counter clockwise will increase the outlet temperature to a hotter setting. Temperature setting per tooth (notch) could result in 4 to 16 degree's based on inlet water conditions.

Check water temperatures to make sure it is at a safe temperature to avoid scalding. Safe operating temperatures range around 120 degree's. Some may have to be adjusted based on season's.
Winter season's when it is cold outside you may have to turn temperature up due to water coming into house will be colder than it would be in the summer.

if you have a single handle tub valve and it starts to not work properly for instance if its gettin less hot water and more cold water it may be time to replace the mixet stem ,what you will need a flat head screw driver a philips head screw driver a pair of needlenose and a pair of channel locks turn off the water main to your home, remove the handle there is a clip at top remove the keeper clip then pull out the old stem take it to your home depot get a new one also get some stem grease to put around the black rubber o rings so your stem last for a long time the grease is also for the handle turns eazy put back in put clip back just remember how you took old one out so it is in the same position turn water main back on and try it out