could anyone please,help i have the above combi it is about 4 years old,and has just started to play up,heats the rads great but when we run the hot water it fires up, water gets hot then light goes off on boiler and then water runs cold for a while then runs hot so on and so on can't even get a nice hot bath full advice please thanks

In ,
sheffielder scribed:
could anyone please,help i have the above combi it is about 4 years
old,and has just started to play up,heats the rads great but when we
run the hot water it fires up, water gets hot then light goes off on
boiler and then water runs cold for a while then runs hot so on and so
on can't even get a nice hot bath full advice please thanks

That's just what I'm getting with my Vaillant.
(See my thread 'Combi Problems' of yesterday)

Seems as I shall be dismantling the secondary heat exchanger tomorrow and
doing a descale with Fernox DS-3 Descaling crystals!

If that is not the problem, then I guess I shall be examining the possible
replacement of the dhw overheat limiter sensor or its associated
NTC-Resistor.

Either way, get it sorted quick before you do terminal damage to the gas
control valve through over activity, as kindly pointed out to me by my
correspondent in that thread! ;-)

hth
N.