I can get central heating to full level but domestic hot water gets only luke warm. Have fitted new heat exchanger to no avail,the setting controls don`t seem to have any effect, what else could be the matter ?
heater is a vaillant combi R S F very old but like a Rolls Royce inside .

james n holbrook, March 2011

You'll have to be more specific about your boiler model, there is no Vaillant combi R S F model as such.
It is old you state, so it could be one of the following:

Sine
VCW
VUW Turbomax

Carefree, March 2011