Came out to call for a system not heating properly. Rental manager stated that the tenant hasn’t had heat consistently over the last few days, and the thermostat was blank. I checked the system over and found the unit tripped on high limit and the blower running. Inspected the system and found an improper size filter and the interior parts of the unit completely caked in animal hair, dust, and debris. Discussed with management about the systems age and condition. Came to the conclusion that they needed repair vs replacement options and she will discuss it over with the owner of the property.