I have two Kohler Margaux shower controllers and both of the value handles are becoming loose. They wobble when touched and seem to have loose connections. What can be done to tighten these up and make the secure???

Check that it's hooked up correctly. I've seen this exact problem when the hot water is hooked to the cold side of the valve.

yes and no. Find hot water heater and insure cold water supply valve is open all the way. check to see if there is a hot water supply value and that its open all the way. If you replace shower value over iron pipe on the hot side it is corroded up replace pipe and value. If copper, find hot side, find value and open it up.

Try to use the user and maintenance manual --->link

u hve to adjust the temprture ring i think u put it all the way so u lock it ,

Try draining the system and apply air pressure (min 30psi) to each faucet. Open other hot water faucets to allow pressure to vent. Next try draining and cleaning the hot water tank.

You will need to buy the o-rings to fix it. You can buy at most hardware stores if you know how to turn off the water you can fix this with more instructions. Let me know if you need more help.

Hired a plumber

The best way is to cut a hole in the wall and fix it right. That will entail replacing the surface material, probably sheetrock. You could try some silicone sealant around the shower arm behind the eschusion. It will still move, but not much.

The device which directs the water up or down is called the diverter. Your diverter is not fully up or fully down. Rather forcefully push and pull the diverter a few times and your problem may be solved. good luck.