I have a Nest thermostat that I am trying to wire in a simple but unique configuration. My apartment uses fan coil units for heating and cooling. The building changes over from hot to cold water for the summer months and back to hot water for the winter months. The old thermostat jumped the Y1 and W1 terminals. When the building changes over for the winter months, the mode on the thermostat is switched manually so the display shows the heating set points, but the same fan that blows air over the cold coils in the summer will now blow air over the warm coils for heating.
Unlike the old thermostat, the Nest does not allow the Y1 and W1 terminals to be jumped. It is programmed to see separate circuits on those terminals that turn on cooling and heating systems, respectively. I want to create a circuit that, when the Nest closes the circuit between the R and Y1 terminal, the fan turns on but the W1 terminal does not have a current. When the Nest closes the circuit between the R terminal and W1, the same fan turns on but Y1 does not have a current. After reading about diodes, I thought that I might be able to use two diodes to make the circuit perform as I described above, but then I became (more) confused when reading about using diodes on AC circuits. Can the circuit be built similar to my picture with the diodes below with a resistor to stop the diode from burning up or am I totally on the wrong track.