When I turn my mendota DV on, I get large blue flames for about 1-2 minutes then they will be snuffed out. Running it temporarily with the glass cracked will "get it started" so to speak and the flames will orange out and it will have no problem running for the rest of the period. This is a relatively new install from last year and after changing the control board and the thermocouple / pilot light its now working correctly. When the weather was warmer it would fire up no problem but now that it's colder I have to run continuous pilot for it even to light right. Am I not getting enough O2 or is the combustion not escaping fast enough? It has to travel up about 15ft out a chimney.