Thermostat Wiring Guide - Conventional Systems Alternate Wiring, Terminal Map

This document is step 5 (continued), "Connect Wires," from a thermostat installation manual, covering "Conventional Systems (Alternate Wiring)." It shows a wiring diagram mapping old thermostat wire labels (C/C1/X/B, O/B/H, Y/Y1/M, R/RC/RH/4/V, G/F, W/W1/H) to the new thermostat's screw terminals labeled O/B, Y, R, G, and W/AUX. Three numbered notes accompany the diagram: (1) Do not use the C, C1 or X wire, and do not use the B wire if an O wire is already present; wrap bare wire ends with electrical tape. (2) The thermostat cannot be used if the old thermostat had any two of the following wires: R, RC, RH, 4 and V. (3) Place a jumper wire between the Y and W/AUX terminals if using a heat pump without auxiliary/backup heat. Despite being filed in a 1979 Chevrolet C/K Pickup gallery, this is an HVAC thermostat wiring instruction sheet, not an automotive document. A reader learns which legacy thermostat wires map to which new terminals, which wires must be capped and unused, an incompatibility condition, and when a Y-to-W/AUX jumper is required.