When we bought the bought one display was missing and the other did not work. Bought just a dis[lay and plugged it in and it did not work in my system. Seems I had the older display passport II legacy with the penguin facing the wrong way. Technical support a Micro air said I needed the control board also 400-IO. Ordered the control board and it was just like they said a drop in replacement. Made surer I labeled all the wires and tool a picture to ensure I got everything right. Installed the control board and used the display I already had from them 402-IO. The A/c works perfectly and even shuts down when it reaches the set temperature. Found my other display (Original) was stuck on cooling and just ran all the time you could not adjust it as it would blank out and stop working. So I ordered another control board and display. Installed and now both A/C units work perfectly and the system is like new! Very pleased there was a solution to make this system work instead of replacing both a/c units and displays. The parts arrived very quickly and in great shape.