Program Number

The program number is a numerical index as to the amount of heating or cooling required to meet the desired in-car temperature. There are 4 variables which determine this number: Set temperature of the CRT, outside temperature, in-car temperature and sunload sensor. The program number controls the blower speed, air inlet and outlet doors, and is also a factor in determining air mix door position.

This number is calculated by the BCM by comparing the in-car temperature with the set temperature, and adjusting the result to reflect the outside air temperature and sunload.

This program number is calculated frequently to take into account changes in in-car temperature. When the in-car temperature reaches the set temperature, the system is in equilibrium and the BCM strives to keep the program number at this point.

The program number is displayed as a number between 0 and 99. A low program number calls for cooling, a high program number calls for heating. The program number can be observed while the system is in the diagnostic mode. Also, when in this mode, the technician can override the program number to observe the effect on system operation.