Performed furnace maintenance on 1998 comfort maker system. Upon my maintenance I came across a few points to concerns that were addressed with Dan. 1. Found that the secondary motor control is becoming weak due to fan motor using more power than needed. 2. Circuit board shows signs of burn marks and overheating. 3. Mercury style thermostat showing intermittent behavior this may due to mercury oxidizing and interfering with 24 v connection. 4. Inducer motor beginning to over amp 5. Indoor blower cabinet has dirt and debris buildup Due to 1 inch filters not efficiently stopping dust 6. Return Plenum and supply Plenum made up of fiberglass ductboard this material tends to break down after five years and will begin to release fiberglass particles into the airstream