Arrived to do a performance maintenance. Started inspection inside and measured a temperature split between return and supply air. Measured power consumption of the blower motor and checked system for cleanliness. Found that the blower wheel is heavily coated in debris. Performed a static pressure test and found that the system was running well beyond the rated maximum. Reached out to a field supervisor to finish the diagnosis on the systems static pressure. Moved inspection outside and verified system refrigerant charge. Verified operation of all mechanical and electronic components of the condenser. Rinsed coil free of debris and removed leaves from the inside of the unit. Found crack on furnace heat exchanger this is a safety concern due to the systems ability to leak carbon monoxide into the home. Air conditioning system is operational at this time.