Hello Niko,
Have you already found a solution?
I have the same furnace and same problem, Error E501 means the PCB is not detecting the flame.
In my case this issue begun a couple of months ago but now seems to be getting worse. Last Friday I had to reset the furnace 5 times and turn it off and on again before attempting to take a shower.
As this is making me mad, I disassembled the boiler and took apart the PCB. I believe that some component has degraded and is causing this erratic failure. I´ll try to fix it tomorrow and post the results.
Kind regards,
Fabian
Fabian, March 2012
