The temperature sensed by the thermostat is higher than the 99 F (37 C) upper limit of the thermostats display range. The display will return to normal after the sensed temperature lowers within the 40 to 99 F (4 to 37 C) display range. Turn on the cooling system or use other methods to lower the temperature. This condition could occur from the system being turned off during an exceptionally warm period or upon installation when the thermostat has been stored for a long period of time in a warm vehicle or location prior to being installed.