Economiser. They have a thermal switch that opens at below a certain temperature to lock out a compressor and opens an outdoor damper to let cool fresh air in instead of cooling it while exhausting return warm air. This at 60*F and below outdoor ambient temperature.
If you read the diagram the outdoor temperature sensor is found there, phisicaly located typical straight down on lower part of the unit or one side.
In case of problem, short the two words together to achieve electrical continuity and to bypass the sensor.
Other type of systems may not apply to this method.