I am able to get hot water as usual but every minute or so the water turns cold for 5 seconds and then returns hot. Looking at the temperature gauge while this happens it steadily increases to 90 degrees until cutting off and going cold (I assume this is the overheat protection kicking in).
Can anyone suggest how I can fix this problem myself, of is it an Engineer/new boiler job?
Boiler model is a Valliant TURBOmax GB 242E.
Thanks in advance
