HVAC 313A schematic bench
Trace the path. Find the fault.
Interactive wiring diagrams for field techs. Line voltage and 24 V control never share a rail. Play Call for Cool, Heat, and Fan — then meter the points that actually decide the call.
Call for Cool · Y path
Power trace
Click a wire. Follow the same label — R, Y, L1 — or walk one hop.
Sequences
Cool, heat, fan. Watch 24 V hit the coil, then 240 V hit the compressor.
Meter points
Expected voltages at the disconnect, R–C, Y at the outdoor, T1–T2.
Photo scan
Shoot a panel or data plate. The bench names the domain and the tests.
Three units. Three different machines.
Full libraryResidential split — 2.5 ton / 80k gas
Outdoor condensing unit plus indoor gas furnace. Classic 24 V R/Y/G/W/C. Contactor, dual run cap, LPS/HPS in the Y path.
Packaged RTU — 5 ton gas/electric
One cabinet on the roof. Supply blower, condenser fans, scroll, and gas heat share the box. Economizer on 24 V. Not a split.
Ductless mini-split — 12k heat pump
Inverter compressor, interconnect 1/2/3, no 24 V thermostat. Indoor is powered from outdoor. Do not land R/Y/G/W on this machine.