"Freedon 90" Furnace Blowing out Cold Air

LAFAYETTEGIRL

I hope someone can shed some light for me. I'm visiting my parents for the holiday and discovered that they've been tolerating a non-working furnace for apprx 5yrs. It's an American Standard Freedom-90 and blows out cold air internittently. They said it happens more when the temp outside gets colder. The company who installed it keep coming out to "service" it at huge fees to my elderly parents each visit. I'm suspicious that they've installed a lemon and are just fixing it enough to show up again within 3mos. Any ideas/comments?