Central heating problem on Worcester 24i RSF

[markadams]

Does anyone have experience of these boilers, it has an odd problem where the Hot water works fine and central heating will not light the burner.

When a CH demand is given, the pump runs, then fan and it goes no further (no spark or opening of the gas valve) I have tested the CH thermistor and it 14.7k (fine), the APS and Overheat stat must be fine as it works perfectly in hot water mode. I checked the harness from the CH thermistor and its fine. The overheat button is depressed.

Other than a very odd PCB fault I cant see what else it would be.

 

[jonnyswamp]

What is the bp when trying to light on heating, min could be too low but fine on high (hot water)

 

[jonnyswamp]

Sorry mods, open forum

 

[markadams]

Its not energising the solenoid in CH mode, No BP on CH.

Mark.

 

[Dotty]

Thread moved.

 

[jonnyswamp]

My bad, I didn't read it properly

 

[newcastle phill]

When on hot water the fan is at full tilt. But when heating first goes on the fan is at a low rate with gas at low pressure before it ramps up.
Are you sure the fan is pulling the APS.

 

[sammathias]

Had the same fault a few months back. thought it was the gas valve harness which it was not. Ended up fitting a 2nd hand pcb i had lying in the shed and off she went!!