Performed furnace maintenance on 2000 comfort maker heaters. Upon my maintenance I came across a few major concerns and safety issues regarding the operation of the heaters. Downstairs- 1. Found that heat exchanger has developed cracks in all four chambers due to overheating. This is left the heat exchanger in a failed condition and is not safe for operation. 2. Inducer draft motor is running at 1.70 A exceeding in specification of 1.60 3. Circuit board has developed heat marks on diode’s and can lead to intermittent behavior and failure for AC and heating call. 4. Temperature rise on system was 75° exceeding the 65° limit this is due to low Airflow and ultimately result in damaging the heat exchanger 5. Static pressure on system is the airflow that was recorded at .95 water column which is an indication the air is definitely restricted considering that the specifications should only reach at .50 wc Upstairs 1. Upstairs heat exchangers also developing small fractures and cracks n