Now, please try again to explain what the problem is, including where the serial data comes from.
I have an Arduino in my observatory in a workshop separate from where the telescope is. It has a temperature sensor and 2 relays connected to a heater and a fan. I have another Arduino in the house 80 feet away across a creek. This one has an I2C 20x4 LCD and two push button on/off switches. They are communicating with each other through APC220 transceivers. I want it so when I want to work out there I can check the temperature and turn on the heater or fan as required. I do not want the room heated all the time, much too expensive( outside temperatures here can go as low as -29F). I have the temperature displaying on the LCD just fine with the code I posted however, I don't seem to get the observatory unit to get and decode commands coming back. I know they are being transmitted because I can see them on another APC220 connected to my PC. I'll just put up with the blinking backlight if I can somehow get 2 way communication working. The code I am sending is 11,- both off 21, heat on fan off ,- 12, heat off fan on,- 22, both on. I tried swapping APC220 modules between the PC and the observatory Arduino, same thing. I delay the second device long enough that the message could be totally there before I look for it. Anything else you need? If I get this working, the second unit will respond back to the first with relayS status, which I'll display on lineS 3 and 4 on the LCD.