Mira Sport shower running cold

I've a mira sport 9KW mains fed electric shower. Since Tuesday it has been exibiting the following symptoms:-
Turn on - power light on - hot water for a few seconds - followed by cold.
The low flow light is NOT on at any time.
No amount of twiddling with the dials will affect the temperature.
I've done the following:-
Thoroughly cleaned the shower head, indeed run the shower without the shower head - in case of pressure build-up.
Ensured the filter is clean and not obstructed.
Taken the cover off and there's no sign of soot (i.e. results of shorting) or dirt.
And now I'm a bit lost. I assume the next thing is to check the electrics and my mira hand-book talks of 'continuity checking' but I'm not at all sure quite what this means and how one would know if a check is 'OK' or not.
Help please
all advice gratefully received.
Regards
Bazza

do you have

Kevplumb,
Yes I have since borrowed a similar tester from a mate and now know what 'continuity testing' means. I've 'measured' across various terminals and got a zero result which my mate tells me means that I've good continuity. I've also 'measured' across other terminals and got no reading - which I understand means no path or broken path. What I don't know, because I'm not an electrician specialising in Mira showers, is whether these other terminals ought to have no path (and by inference are OK). ?!
So I'm not sure where I stand

all depemds which terminals your belling across

some are meant to be open

one assumes you have the mi's

follow the internal wiring diagram

if you can't get somebody that can

that electrikery stuff hurts if it bites

your jumping in head first.

you say its hot for a few seconds then cold.
is that every time you turn it on ? or is it just cold now all the time ?

been waiting for you karl

i'm awake now