I called the Grohe technical support office in their US headquarters and spoke to a Joseph there who guided me through the process, which is quite simple to do. Make sure that you have a thermometer available to check and calibrate the temperature to.
First carefully remove the small plastic tab at the end of the thermostat handle control and put it in a safe place. It can be remove with a finger nail or small flathead screw driver. Then inside there is a screw. With a flat head screwdriver, remove the screw and put it in a safe place. There should be a large plastic valve there, probably black. Turn on the water to the handheld shower. Turn the black knob on either clockwise ( to the right) or counter-clockwise ( to the left) while holding the thermometer and your hand under the water so that you can feel and watch the temperature go to the 100 degree mark. When it hits that temperature, do not turn the black knob anymore. Replace the cap and make sure that the arrow on it is pointing to the 100 degree mark and replace the screw. Then put the plastic end cap on. You should be able to take a shower now without getting scalded. The same instructions apply if the water is too cold.
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I called the Grohe technical support office in their US headquarters and spoke to a Joseph there who guided me through the process, which is quite simple to do.
Make sure that you have a thermometer available to check and calibrate the temperature to.
First carefully remove the small plastic tab at the end of the thermostat handle control and put it in a safe place. It can be remove with a finger nail or small flathead screw driver. Then inside there is a screw. With a flat head screwdriver, remove the screw and put it in a safe place. There should be a large plastic valve there, probably black.
Turn on the water to the handheld shower. Turn the black knob on either clockwise ( to the right) or counter-clockwise ( to the left) while holding the thermometer and your hand under the water so that you can feel and watch the temperature go to the 100 degree mark. When it hits that temperature, do not turn the black knob anymore. Replace the cap and make sure that the arrow on it is pointing to the 100 degree mark and replace the screw. Then put the plastic end cap on. You should be able to take a shower now without getting scalded.
The same instructions apply if the water is too cold.
There is a stop underneath the handle,its set to stop before water gets to hot anti-scald can be adjusted for hotter water