baxi 105he problem

[jamescwakefield]

hello all

when I turn switch round to central heating

the power light comes up, boiler seems to come alive

but the tap light next to the power light keep flashing the boiler sound like it going to fire up but then light flashs and it like it resets itself and tries again?

any ideas?

from further inspection the rear micro switch behind the diaphragm keeps opening and closing as button flashes


when having switch to just taps the water never gets hot
the front micro switch opens only boiler doesnt fire up

any ideas please?

 

[Wongfeifox]

A flashing dhw led means that the preheat function is trying to come on, I'm guessing it is an instant model with the preheat ?
However this should also be the same in just dhw mode.
If the flow switch makes on the domestic side then does the pump run ? If so try lifting the primary flow switch to make the switch manually, does the boiler fire ?
There is also a small orifice in the bottom of the primary flow switch diaphram housing unit that can become blocked resulting in lack of primary flow switch making, or a basic check is make sure the auto air vent on the pump is open, almost got caught with this last week.