HELP PLEASE.Hi there,i have a biasi garda he combi boiler that was working fine until earlier in the week when i started having problems.The hot water runs hot for a few seconds then tepid then hot but not enough to be able to run a bath.the temperature gauge will go from 60-90 then back down again.I have noticed that the sequence of lights shows d.h.w operation excessive temperature on primary circuit fault.Can anyone please tell me how to solve this problem or whether i need to call a plumber out??? THANKS.....