Originally Posted by
KC13
Some of them look like a sure thing, some may require a little investigative work on your part. The "solids": Red to "R", green to "G", yellow to "Y1", white to "W2" (may require jumper to "E", stay tuned), orange to "O". The "iffies": Blue and brown. Here comes the "gumshoe" part: Locate where thermostat wires connect to indoor unit (if split-system) and note letter designation of terminals where blue and brown connect. If connections are not identified, some studying of the unit wiring diagram will reveal the answer. Post results.