Glow Worm Ultimate 40FF ~ Intermittent Fault

[Evilshrew]

My boiler wont ignite.

It has been an intermittant fault of the fan "hunting". Sometimes the boiler sits in this loop but sometimes she blasts up.

I have stripped and cleaned the boiler parts (not desturbing the gas parts).

I have checked the air pipes both positive and negitive and there seems to be no issue with thro' flow.

I have now got to the control box and checked the Air Pressure Switch (202201) and it is tripping the PCB. I bypassed the APS but the fan ran continually but the unit did not light.

This leaves me with 3 components that may be at fault. The APS, PCB (900847) or the Multifunctional Control. I am assuming its not the MC otherwise I may as well just get a new boiler but can anybody help in diagnosing this problem.

On inspection (and reading other discussions) the PCB is a 2 fused, Yellow LED type (so possibly the old version with the pants design flaw).

I need to know if it is worth getting a new PCB and the APS or just the PCB. Or if I am totally barking up the wrong tree....

Any advice would be appreciated....

 

[Rob]

Had exact fault little while ago. Was advised by GW technical to check the pump resistance.

If the PCB sees a funny resistance it will cause the fan hunting.

It was the PCB at fault as is yours probably.

 

[Evilshrew]

Chaps,

To let you all know I changed the PCB and the boiler fired up first time.

It was easy but I took a few pictures to ensure all the wires were correct.

The PCB (900847 ~ 2 fuse type; 105111) was ordered on Sunday night from www.keeptheheaton.com and it arrived on Tuesday afternoon, fitted tuesday night (20mins).

I also orderd a thermister control (112085) but this is only needed for the upgrade from the 1 fuse type. Still a spare is not a bad thing...

Anyway this helps if you have a similar problem.

Happy heating.