Hi there,
It sounds like the Nest isn’t detecting your Y2 wire due to either a wiring connection issue or a compatibility concern. First, double-check that the Y2 wire is securely seated in the terminal on the Nest thermostat. Sometimes, even a slightly loose connection can cause the thermostat to grey out the wire. Next, verify that your system is fully compatible with Nest. Not all HVAC systems with multi-stage cooling (Y2) are supported without adjustments, so it’s a good idea to run your setup through the Nest compatibility checker.
If the wiring seems fine and the system is compatible, you could try running the wiring diagnostics in the Nest settings. Occasionally, resetting the thermostat or removing and re-adding it to the system can help it detect wires correctly. If the issue persists, it might be worth testing the Y2 wire with a multimeter to ensure it’s carrying voltage as expected. In some cases, wiring setups differ slightly between Honeywell and Nest thermostats, and you might need to make minor adjustments.
If none of these steps work, reaching out to Nest support or consulting with an HVAC technician could save you time and effort. Let us know how it goes! Good luck getting everything up and running!
