possibly aproblem with the flow control valve in the shower. To test switch shower to cold setting and operate the flow temperature control over full stroke.
This should adjust the water from the handset.
Try setting the temperature control to a cooler setting, if the shower output then warms up adjust the temp setting slightly to see if you can keep the shower at preferred showrring temperature
If not you should consult with an electrician
garryk
February 2010
Automatic Answer
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