Scratching my head Worcester heat-slave fault

[TFGplumbing]

Hey guys hows it going? need a bit of help did not want to post in the public oil forum & its not a gas boiler so here I am.


Greenstar Worcester heat-slave 18/25 oil

Went to Look at a leaky boiler today - No prob's, leaking flow switch remade joins shes okay no leaks.

Go to recommission the boiler, turned her on set both the boiler stats HW & CH to about 3.

Waited for about half hour, fecking thing is still running, another 15 mins.... still running(the boiler was warm when I arrived) Room Stat is not calling, Hot tap not running. Heat bank in boiler getting a little bit too hot for my liking.
So I turn Both the boiler HW & CH stats to their lowest setting & made sure the room stat was not calling, Shes still running.
The rads are getting bouncing even though no stats are calling. The hot water comes hot for about 30 seconds the goes luke warm.

What do you guys think? I'am thinking that the CH micro switch on the diverted may be stuck on.

Anyone come across a fault like this before, its not often I come across a boiler that wont stop running.

cheers

 

[Leo21]

On the gas ones, the heat store of hot water scales up. You get a bit of hot water then it goes cold. If that's the case the boilers an uneconomical repair. I've seen it at least five times.

 

[Nostrum]

Had problems with those paddle flow switches before, did you take it out? Sometimes they jam open and the boiler thinks h/w is being called.

 

[TFGplumbing]

Had problems with those paddle flow switches before, did you take it out? Sometimes they jam open and the boiler thinks h/w is being called.

Yes I took it out and the "paddle'' seems to move freely back and forth, no scale, tested it with the multi meter and the switch is okay.

 

[TFGplumbing]

This is the flow switch assembly

WORCESTER GREENSTAR/HEATSLAVE FLOW SWITCH ASSY 87161114060 NEW | eBay

 

[Roger Welton]

The paddles stick for a past time on these.

 

[TFGplumbing]

Hmm I was just wondering, how these paddles actually return to the switch off position, onnce the tap has been turned off?

Thanks for the posts btw guys

 

[Leo21]

Can't you do a continuity test on it?

 

[TFGplumbing]

Can't you do a continuity test on it?

Yes I've done this, with the switch detached from the boiler. Swtich is okay perhaps its sticking once connected to the CW.
Assuming he switch is sticking open constantly, how would this cause the HW to stay to for 30 sec the go luke warm?

 

[Leo21]

It might do, if I remember right it has a hw pre heat. So the store would be exhausted quickly. Isn't there a connecter so you can test the switch in situ? And also isn't there's tell tale light on the control panel when hw called for?