when pulling the cord to turn the shower unit on which is attached to the wall which provides power to the shower unit, the red light on the wall box goes red as normal to indicate the shower has power and is ready to use.

but once the power button on the shower unit itself is pressed to start the shower the red button on the wall with the cord goes off so the shower doesnt start.

shower details are as follows

redring expession 500

william, February 2011

It sounds like you could have an earth fault on the shower unit or the heater can element has broken down and is earthing out, does it trip the MCB?

Foggy, February 2011

electricians job to find fault.
Dangerous if you don't know what you are doing and to post the question you don't.

UK part P electrical installations say you can't work on electrics in direct wet contact areas including kitchen or words to that effect.

bb, February 2011