Ravenheat RSF 84E (T) Boiler problems

Help!
This problem started over a month ago and i have had an Engineer out on 4 different occasions. Initially i had no heating, the boiler was failing to ignite when used in hot water & central heating modes.

1st Visit: The Engineer repositioned the spark electrode although the ignition display indicator never lit. Working fine whe left.

2nd Visit: A week later same problem again, and again repositioned the spark electrode but left with a recommendation that the air pressure switch be repalced. At this point the ignition display indicator was still not lighting up when firing. and the firing mechanism intermittently turning on and off.

3rd Visit: Replaced the switch. When in use the same day intermittent problems again.

4th Visit: Concluded the problem lies withinthe control PCB as he seen a relay with looked defective, showed signs of wear. I am handy with electronics so i replaced the relay, and the still problem not solved.

My question: should i fork out another £150 to get the PCB and will this resolve the problem. I am not sure i can trust the engineers recommendations. I have spent so much already, is this a competence issue with the engineer?

Intermittent symptoms, with multiple things wrong causing those symptoms, can take a lot of time money and persistence to sort out. I'd be calling thetechnical help line at Ravenheat, they know the common failure points and can clarify the detailed sequence of operating which isn't always obvious from the book.

Ignition and flame sense leads cause this problem on these boilers,try replacing very cheap, as you have to gain acess to boiler compartment cogi job only

Visit 1- The spark electrode sits in a pocket and is secured with a capnut. The tip on the electrode is miniscule, so it cannot and should not be bent. I went to one of these boilers to find the electrode snapped in two

Visit2. If air pressure switch were defective, ignition sequence would stop at fan run i.e. no spark at the pilot burner.

Visit 3. Clearly a part has been changed without reasonable diagnosis.

Visit 4. Fishing

I have just cleared a defect on same boiler (north side of Glasgow- very similar story- wonder if it is the same boiler). The gas valve was defective. Upon examination of gas valve, notice the gauze filter was ripped with tiny threadlike fragments at the rip. Wonder if these entered the gas valve to create a problem.