I have a Ruud central system. Gas heater. Closet installation with air intake below. The A coils are above the unit just below the attic. The A coil compartment was sealed with some type of sealer over tape. I removed some sealer and found a removable opening from which I can see the A coils but, I cannot access the underside of the coils which I am sure need cleaning. I also see a side cover but there is no room to work from there. It sure seems that major disassembly is needed meaning removing the firebox. Any hints ?