Boiler Fault - Sime Superior Mk 2 - Suspect gas valve?

[scratch339]

Excellent, near freezing outside and the boiler has packed up

As per title, it is a Sime Superior 40 Mk 2 gas boiler. I Think its about 6 years old, but we only moved into the house a few months ago. It has not been serviced yet

It has been running fine until tonight. Now It wont fire up!

The fan will run, then you can see/hear the ignition sparking... but no flames. It then switch's off and the Lock-Out button illuminates.

The gas supply is fine. I took off the PCB cover, and checked there was a 230v output to the gas valve solenoid at the correct part of the fire-up sequence. There was.

Checked for continuity/resistance across the solenoid. Nothing/infinity.

Assume from this it is the solenoid, and therefore the whole gas valve that is knackered? As a side note, there is a push 'button' on the solenoid... is this some type of manual override/operator? doesn't do anything when i push it (even during the fire-up sequence), just moves 1mm or so.

As for possible causes to the whole problem, i have been chasing out walls in the room so it has been VERY dusty. When i took the cover off, though, didn't seem to be that bad around the controls area.

Any comments or help would be grand. Thanks

 

[Agile]

If the gas valve solenoid is really o/c then its reasonable to expect that its failed.

Depending on the type it may be possible to just change the solenoid. Can you post or email me with a photo?

A gas valve should be changed by a competent CORGI who knows how to set it up after fitting a new one.

Tony

 

[scratch339]

Thanks for the reply Tony,

The Gas valve part number is:
(Sime) 6243815
(Honeywell) VK4105C
(Halstead) 988302

If the solenoid CAN be changed, is it a standard part ie will an engineeer have it 'in the van' tomorow? neeeed heeeeat asap

 

[Agile]

I dont know if the solenoid is changeable on your model.

Similar VK4105 gas valves with a seperate modulation coil do have replaceable solenoids similar in appearance to those on yours. Few engineers would carry that spare coil assembly unless they were service engineers for a model that used it and in any case as far as I know for all warranty calls the whole gas valve is replaced.

However, your valve uses one of the coils as a modulation coil by applying a pulse width signal to it.

My expectation is that the coils would be the same but....

Which coil is o/c ? Whats the exact resistance of the good coil?

Tony

 

[scratch339]

As it worked out, you cant buy the coil only for this vaLve, so had to get a whole new gas valve

The new valve wasnt for my model boiler, but the coil was the same. Actual unit wa the same price as the proper SIme one so made sense to get the new unit, and change the solenoid over. That was i didnt need to reset-up the max/min jet screws & gas flow rate, which would be outside of my capabilities

All good now, though. We have heat again. Thanks again for your help Tony.

 

[Agile]

Which boiler was the valve for?

Could you measure each coil resistance for me on the new one.

I am interested to see if they appear to be the same as the other type.

Tony

 

[scratch339]

Sorry tony, the coil was put on before i saw your post.

thanks for your help though

 

[Agile]

If you ever have a moment to open it up again then I would still like to know the resistances!