Rolo,
See my YouTube channel below. I have five videos showing how to troubleshoot your heater, replace the pilot generator (powerpile/thermopile), jump out faulty sensors and some tips and tricks to cleaning out the terminals and connections.
Post any questions you have here, I'm somewhat of an expert in troubleshooting and changing out parts on these heaters, I've rescued a few of them destined for the scrap heap because the owners had given up on them and it turns out a good cleaning or some sensor replacement was all that it needed. These videos are my personal H350 heater that I've nursed back from the dead and kept running for about 14 years now.
I realize this is my first post on the forums, let me know if anyone else needs help in getting these millivolt heaters running reliably.
https://www.youtube.com/channel/UC0PbutcEjwd0OC4RUZfVflA