PPRUNE is an absolute gold mine of information. I am happy to leave my engineer to look after the mechanics of the aircraft as his knowledge is far greater than mine. I thought it interesting about the advice to not fly the aircraft with a faulty gauge. I am not sure I agree in this particular instance as it is only a gauge and if all other indications are correct then continue. My ears and eyes will suffice in place of a faulty gauge at least on a temporary basis but of course that is also dependant on which instrument is at fault.
Thanks to one and all for the information.