Worcester Bosch 24CDi RSF Problem

[monkeylovin]

Hi all, I am a corgi registard engineer and was wondering if there are any other enginners that have come across the same problem on the above boiler. I was called out to this boiler with the fault lights telling me that there is a primary overheat. I have changed the sensors on both the central heating side and hot water side but still have the same fault. When the lights flash the pump pulses with the lights which indicate that the pump works and when you call for hot water the fan runs also which again indicates the fan is ok. The only other thing that happened when it first stopped running , it released alot of steam from the auto air vent. I am now assuming that it is the PCB but wanted to get some more opinions before i replace that expensive part! Many thanks in advance. Mark

[lembo121]

Hi Mark,

If the A.A.V is spilling steam the water inside the boiler is not moving when the appliance is on. Im thinking one of the following faults.

1) Faulty pump! Although the pump seems to be working, the spindle might have detatched from the main arm.

2) Blockage in the heat exchanged.

3) No by-pass fitted and all the trv's are off.

What ever the problem is, its NOT the P.C.B. Don't change it! its not going to resolve the problem!

Your problem here is definatley a circulation fault.

Good luck.

Lembo121

[monkeylovin]

Hi Lembo121,
Thanks for that answer mate, would those answers still stand even if the central heating was not running at the time? The boiler was heating hot water when it stoped working and released out of the AAV. Would it be using the pump for hot water being a combi? Im thinking you are right on the circulation fault.
Thanks again.
Mark

[lembo121]

The boiler does use the pump to heat the hot water.

It circulates the same water that heats the radiators into a secondry heat exchanger. This then heats the domestic hot water.

How's the temperature of the hot water?

[monkeylovin]

Hi lembo121, Temp of water was normal before it stopped. it just stopped half way through a shower. the heating was not running at the time. I spoke to worcester technical today and they tell me that it could be the pcb. Nightmare!!