Temperature controlling for a transport refrigeration system

A load temperature controller for a transport refrigeration system having heating and cooling modes, and high and low speed modes, comprising:

• selector means for selecting a set point temperature within a first predetermined temperature range,
• sensor means for sensing the load temperature,
• means for providing an analog ratio between the selected set point temperature and the sensed load temperature,
• means providing first and second analog reference signals,
• comparator means for comparing said first and second analog reference signals with the analog ratio to detect failure of the sensor means,
• converter means for converting the analog ratio to a digital signal having a predetermined number of bit changes between all logic ones and all logic zeros,
• said converter means scaling the conversion such that all of the predetermined number of bit changes occur within a second predetermined temperature range relative to set point, with the second predetermined temperature range being smaller than the first temperature range,
• and logic array means having inputs responsive to said digital signal,
• said logic array means being programmed to provide a plurality of transport refrigeration system control signals in response to predetermined values of the digital signal.