HVAC, Interior, and Passenger Amenities
Comfort and accessibility
HVAC inspection is a performance test, not just a visual one. On the cooling side, verify compressor drive belt condition and clutch operation, condenser cleanliness, and airflow. A condenser packed with road debris raises head pressure and kills cooling capacity while the refrigerant charge is perfectly fine. Check the receiver-drier, sight glass if fitted, expansion valve, evaporator coil and filters, blower motors and relays, and return-air grilles. Measure vent temperature at the duct with the blower on high and doors closed; a drop of roughly 35 to 45 degrees F below ambient is the rule of thumb for a healthy system. Never open a system without recovery equipment, and never overcharge to make it colder.
Heating and defrost: check coolant flow through the heater core, the control valve, and blower operation; the defroster must clear the windshield as designed. Test the engine preheater and the passenger-area auxiliary heater, including fuel lines and exhaust, for leaks.
Passenger amenities are safety items on a transit bus. Verify the wheelchair ramp deploys, stows, and interlocks correctly; the kneeler operates; securement tracks and belts are intact; stop-request cords and signs work; emergency exits, windows, and hammers are unobstructed; interior lighting, PA, camera, and fire suppression function; and seats, stanchions, and handrails are secure with no sharp edges.
Worked rule of thumb: a not-cold-enough complaint on a clean-looking system usually means airflow, so check filters and blowers before refrigerant.
Trap: do not sign off an accessibility device because it moves; it must complete its interlock cycle.