Arrived to do a performance maintenance. Set up for combustion analysis temperature split and static pressure tests. Found that the system is operating with a very high temperature split. This causes the heat exchanger to wear and tear faster. Verified operation of all mechanical and electronic components of the furnace. The igniter is testing well but can see the crack forming where it will eventually break. Checked blower for cleanliness and to see if there is any play in the bearings. Found that the fan for heating and cooling is heavily coated in dust debris. This is likely what’s causing the system to operate close to overheating. Checked systems heat exchanger to ensure proper venting of flue gas. Found that the heat exchanger is cracked and is completely covered in heat stress. This makes the furnace unsafe to operate in heat mode. Performed an electronic gas leak search. Reviewed the maintenance and shared recommendations. Signed red tag with homeowner. Homeowner mentioned how