BAXI Luna 310 Fi

iceboater

Problem with my BAXI Luna 310 Fi. I use it for both hot water and radiant heat. I installed it myself about 10 years ago, replaced the PCB about 5 years ago.  Here is the current problem:  It will cycle for about 30 minutes fine, then it will overheat and not shut down even when the temp. goes up.  I believe this is also called a failure to modulate?   It will then blow off and shut down and gives a fault code of either 6 or 8.  Sometimes it gives the pilot fault code and sometimes the fan.  Thoughts?

Also how do you clean out the venturi and where is it located?

many thanks.