Upon arrival tech was informed that the blank thermostat was for the older system that served half of the showroom. The power was cut off at the disconnects for the condensing units at a request of the customer due to renovations on that side of the showroom. Tech restored power and verified the thermostat powered up. Tech did check on the newer system due to the history of the system. There was some adjustments made to the system and it was operating upon departure.