Hey guys, I have a Trane XL-12000 gas pack unit with a heating problem. Sometimes the unit runs fine and at other times it won't. The unit is calling for a new board, but I'm wondering if there is something else going on with the unit. Like I was saying sometimes it runs fine and will get the house up to temp. Other times it will come on for a few minutes and shut off, while the t-stat is still calling for heat. It has more problems the colder it is outside. I have checked all of the safeties for continuity and all checked out fine. I pulled the flame sensor out and cleaned it, not that it was really in bad looking shape anyway but I thought it couldn't hurt. I'd appreciate any ideas on what to look for. Oh and yeah I'm a HO that has hung thousands of feet of duct work (mostly commercial) so I hope that will keep me in your good graces with out the HO barbs, LOL! Thanks again with any advice.