I'm trying to found out if there is a clog somewhere prior to calling hvac in. I kind of remember having an issue last year and the repairman pulled out a glob of dust thing. I can't locate a diagram on line for this unit, and I don't want to randomley start unscrewing everything to get electrocuted . I am a woman and need help explained in detail argggggg thank you so much... please help. It's a Beckett model afg ou201 oil forced. Thanks :-)