Worcester bosch 24CDi RSF Problem

[monkeylovin]

Hi all, I am a corgi registard enginner 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

[mattfox]

I deal with about 12 engineers as I work in a council housing dept... I'll print your question and ask them on Monday, unless you get any more replies in the meantime!