Tried searching for help, but thought maybe my case was a little different. My carrier furnace is yeilding a LED code 31 after multiple turnoffs and turnons. Tried fuse switching and had some duct cleaners out who cleaned out a lot of stuff (recently flipped house). Fan works, AC works, but flames wont ignite. Im not a proffessional, nor do I remember the cleaning crew going on my roof (though the exhaust and intake might be on the side of the house under the porch). Should I look into calling a professional, ie for a new pressure switch, look at the filter, or take a whack at the exhausts and intakes on the roof or under the porch (behind some cheap wood grating)?