Clicking Worcester 2.4i RSF

[onejontwo]

Any heating engineers out there for advice please?
The problem I have is that on my Worcester 2.4i RSF combi boiler, every now and again it seems to fire up and turn off in quick succession, some times it's fine for a while but once the boiler is fired up for the heating and the water is demanded, this is when the symptoms mostly occur. The radia
tors get hot and the water gets hot, but the switching on and off worries me!
I am a mechanic by trade and have serviced the boiler as the instruction manual (I know I'm not supposed to touch it unless I' m Corgi registered but I'm not exactly flush at the moment)
I'm no gas engineer but my mechanical experience tells me it's some kind of sensor fault, but which one??
If any of you knowledegable people out there point me in the right direction, I would be willing to replace the faulty part if it's within my competence.
The reason I don't ring B gas or N power is I just KNOW they'll turn up and say I need a new boiler for the sake of an inexpensive part!
One person suggested a divertor valve diaphragm as a common fault but this model doesn't have one so no joy there!
The hot water and heating are fine apart from the constant firing up and switching off which occurs every 3 or 4 seconds and also is accompanied by a constant clicking noise at the same time of switching on and off.To give you an idea of what it's like, if you switched the temp. switch back and forth in so doing causing the boiler to fire up and switch off, then this is what it appears like but a lot quicker in succession. You can actually see the burner ignite, 3 or 4 seconds later go out, 3 or 4 seconds later ignite again then after 4 or 5 times it will stay lit for 20 mins. or so and then repeat these symptoms again. It seems to be worse when both the heating and hot water are demanded.
It appears to be a fault that is developing ie. getting worse over time.
I hope this makes sense.
I hope you can help

 

[Rob]

PCB are notorious for this fault. But would be worth checking the correct workings of the temp sensors and the APS.

 

[onejontwo]

PCB are notorious for this fault. But would be worth checking the correct workings of the temp sensors and the APS.

What's the best proceedure for checking those? Would I need a professional to check them? and possibly specialist tools?

 

[Rob]

With a basic DMM you could measure the resistance of the APS contacts. Should be almost zero.

The APS is what tells the pcb the fan is running. If this is beginning to fail you could expect for the boiler to drop out and back in again although it wouldn't be instantly as your describing.

Again with the temp sensors. If they were beginning to fail the boiler would drop out and have to go through a sequence again perhaps.

Ive seen this fault dozens of times. Always the PCB.

Also this part retails at £160. Getting BG out on a fixed price repair will be similar so id recommend this. I doubt they'll try and sell you a new one. Its pretty reliable and basic.

 

[onejontwo]

What kind of price are we talking about here? and is it a fairly straightforward job?

 

[Rob]

As i said with the price of the part etc your better off paying someone like BG who will do a fixed price.

Its straightforward if you can isolate and work on electrics.

 

[onejontwo]

With a fixed price repair would this be included in the price or added to it? Also you said they wouldn't try and sell you a new one ? Would they repair the pcb or am I getting confused?

 

[Rob]

Fixed price includeds parts so the pcb would get replace for probably the same price as you could buy it from a shop

Go on their website and it will explain it!

 

[onejontwo]

Thanks for the help Rob, much appreciated, one last thing though, at the moment everything seems fine with no clicking and firing on/off, are these still the symptoms you would get with a faulty pcb?

 

[Rob]

Yeah, pretty much. Could be affected by heat etc.

Let us know how you get on.