Report "My Mr Heater MH9B has run with no problems for two years. Recently it started shutting down for no apparent reason.Closer inspection of operation shows the pilot flame starting out long enough to cover the tip of the thermocouple but 20 minutes into nomal operation the flame gets smaller and does not cover the tip of the thermocouple resulting in a loud click when it shuts the heater down. I see no way to adjust the length of the flame or to change the position of the themocouple and the flame so it covers the tip. What is going on? How can it run nomally for 20 minutes and then refuse to operate, especially since it has run for two years without problems?"