Potterton Profile 40e - Firing up problem

[Stjamespark]

Hi all,
After some help here. I have done timings of events when boiler fires up from cold (start of program):

09:17 Boiler fired up all ok. Set to Max
09:30 Boiler switches off. Outer casing hot (probably normal)
09:31 Boiler tries to fire up. Sounds like relays/valves are working. Fan starts for all of about 1 sec. this continues for about 10 attempts till finally firing up.
So at 09:33 the boiler fires up properly.
09:37 switches off
09:39 same as 09:31

Note when boiler starts first time from cold it heats to thermostat setting on boiler. I replaced the PCB a year ago. New pump installed a year ago (in airing cupboard).
The issue has started in the last couple of weeks. Once fired up it does the job of CH & HW.
Boiler is approximately 20 years old. No unusual noises thankfully.

Thanks

 

[MeldrewsMate]

I suspect that, despite changing it a year ago, that control PCB is faulty.
You can usually hear a relay clicking in and out in time with the fan starting and stopping.
It'll get steadily worse.

 

[Mottie]

I changed the PCB three times in my profile 60e in my 25 years ownership. Same symptoms as you had. last one I bought from a plumbing merchants on a Christmas Eve and I seem to remember paying £220 for it as it was a genuine one. When I replaced the boiler a few years later, I sold the PCB on eBay for more that you could buy a pattern part one for. I think I got about £60 for it.