Repair or replace defective parts in units and equipment and their controls,including thermostats, automatic switches, fan controls, log switches, dampermotors, louvers, relays, filters, controls, belts, compressors, heat exchangers, highlimit controls, pressure controls, safety valves, and automatic gas valves. Inspect, repair, modify and install HVAC equipment including refrigeration and air conditioning compressors, receivers, condensers, chillers, water cooling towers, forced air converter units, pumps, automatic and hand valves, expansion valvesand capillary tubes.