Make sure the power the (double pole power switch ) pull cord on the bathroom ceiling is OFF. Set the Hot and Cold indicator knob arrow between the Hot & Cold position to preserve the original setting.
Remove two screws from the outer top housing and one below the housing.....pull the housing case forward and remove.
Take the shower head out of the wall bracket, and place it in the bath or area where one stands when showering.
WITH CAUTION and not touching anything internally switch the shower on, and observed where the water is leaking from inside the case.
Leaks can come from any joint where the water is feeding into the the unit. The 400x is prone to leak from inside/behind the seal where the toothed gear turns when adjusting the tempreture.
From what I see in the spare parts list this component does not appear to be in the list, but phone the service dept on the gainsborough site as this may have been added later.
One cause that is often overlooked is the mains pressure which in some areas is too high, this is usually indicated by cold water when using a normal sink coming out with excessive force. Locate the (mains water cut-off tap control), and adjust this to a reasonable pressure by turning the tap, and clockwise. Retest and see if it still leaks after checking out other points. Note when the cover is removed, mark the plastic gear with a felt tip pen centrally at the top, to preserve the register of the case control which you set before you removed the cover. I have had two of these units in 12 years, and found them most efficient and reliable. If my latest one ever failed I would not hesitate to replace it with a later Gainsborough unit. regards LVH.
LV Hackney
April 2008
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