2004 high-efficiency furnace — first-time maintenance visit. Performed full diagnosis and complete cleaning, including burner compartment and flame sensor. Verified all safety controls, pressure switch operation, ignition sequence, and temperature rise — all within manufacturer specifications. Noted that the venting is old ABS material with minor corrosion beginning around the elbows, though nothing currently concerning. No signs of water damage or overheating observed. Combustion readings are good, and overall the unit is operating normally. Advised client to continue changing filters regularly and to schedule yearly maintenance due to the age of the system. If any major repairs become necessary, replacement should be considered given the furnace’s age and potential for limited parts availability.