Control Head: Notes

NOTE: The control head and programmer are not serviceable. If for any reason they must be replaced, an exchange unit must be obtained from an A/C Delco Service Center.

The control head used on Electra and LeSabre wagons, and all Regal and Skyhawk models is housed in a plastic box mounted to the instrument panel. The control head faceplate contains A/C mode control, blower fan control and temperature guide setting switches.

These low current switches transfer the control selections to the microprocessor which serves three functions. They execute the selection through power transistors, remember the last temperature and blower selection ordered, and display (via LED annunciators) that previously made temperature and blower selection the next time the ignition is turned on.

In-car temperatures are controlled in all mode positions: "HEAT", "ECON", "AUTO", "BI-LEV" and "DEF". A timer delays blower operation for approximately 3 minutes after the ignition is turned on and the control head has been set to either "HEAT" or "BI-LEV" modes. Yet, the blower fan will start immediately in the "DEFROST" and "A/C" modes.

The control head on Electra and LeSabre sedans consists of 3 electronic printed circuit boards, housed in a plastic box attached to the instrument panel. Two circuit boards, the main central processing board and the digital display, connect to the controllers faceplate. There are 14 soft touch key pad switches on the flat surface membrane faceplate. Each of these address the microprocessor. The microprocessor has both Random Access Memory (RAM) and Read Only Memory (ROM).

The RAM memory stores such information as the present operating mode, position of each valve opening within the A/C module, calculations made by the arithmetic logic unit and the current in-car and outside air temperatures. The ROM retains in memory the last mode settings selected before the vehicles ignition was last turned off.

On all models except Skyhawk, 3 connector bodies attach to the rear of the control head.