Is it normal to have thick black buildup behind ash pan,it's hard to scrap off with a putty knive,but does come clean just a pain to scrap,I've noticed it on the front of door sometimes but not as thick,thanks guys.
Can't imagine Ash think enough to scrape with Puddy Knife. Mine is like fine fluff (grey). Only time it was black was when I left the metal cloth in the pipe outside to block stupid birds in spring. Air was blocked in the pipe by smoke settlign on the wire cloth. You have flapper on the OAK (Outside Air)? Make sure that is working right. I solved mine by fully opening the flap with strong magnet. Then I remembered the cloth.
The company that installed it says it's ok,it's only on the back bye the bracket where you clean the fan and pipe,the sides are fluffy ash I can remove with paint brush,but back is like it's baked on,anyway thanks for the feedback, it's appreciate.