Hello people,

I've recently encountered a puzzling problem with a Vaillant GB 242 .
Hot water works fine, but on calling for central heating the boiler
appears to be dead. There is no roomstat and on on operating the
external programmer I can hear a relay click inside the boiler control
box. On switching the boiler off at the spur and on again the boiler
will fire up and I then get central heating for about a minute, the
boiler then shuts down again.

I'm inclined to think its an electrical fault maybe the heating
thermistor being out of range, but since I don't know what the correct
resistance of it should be I can't draw any conclusions. I assume the
overheat stat will prevent the boiler firing up in both hot water and
heating modes? so I can't imagine it is that. Any experts around ? I
deserve an easy boiler after my last (successful ) escapade with an
Isar.

Perplexed

Heeley