Hello fcaselli,
It sounds like you're having some trouble with your Nest Learning Thermostat, and I'm here to help you troubleshoot. It's great that you've already done some testing and provided detailed information about your wiring setup.
Let's make sure the thermostat is properly connected. It's good that you've set Y1, G, OB, W1, and Rh according to your wiring. However, the mention of switching from Rh to Rc due to a connector in your last thermostat may be worth revisiting. Make sure you have the correct wires at the corresponding terminals.
If the fan is running but only cold air is coming out, there could be an issue with the heat source. Since you've tested the heat pump and aux heat, it's a good start. Ensure that the thermostat settings match the type of heating system you have. You mentioned switching "O" to "B" within settings; typically, if you have a heat pump, O is for cooling and B is for heating. However, this can vary depending on your specific system, so refer to your HVAC system's documentation or contact the manufacturer for guidance.
If the issue persists, it might be helpful if you could share with us a photo of your old thermostat and Nest Thermostat's wiring setup. Also, tell us the make and model of your HVAC system.
Best regards,
Mark
