Self-Diagnostic Mode
DETERMINE SYSTEM FAILUREDetermine whether the operator complaint is due to a system failure or improper operation of the ATC system. It is possible for the system to go into a maximum heat or cooling mode that will rapidly change the passenger compartment comfort level. This hap- pens if the operator changes the selected temperature setting by four or more degrees.
CHECK COMPONENTS
Check the coolant level, refrigerant charge, drive belt tension, radiator air flow, radiator fan operation and air suction of In-car Temperature Sensor/Aspirator Assembly. To check air suction of the Aspirator, place a small piece of tissue paper over the Aspirator opening on the instrument panel. This opening is located to the right of the steering column. The tissue paper should cling to the opening if system is funtioning properly.
BEGIN TESTING
Bring the engine to normal operating temperature and proceed with test and diagnostic procedures. Always test the entire system after each repair has been performed.
ATC COMPUTER DIAGNOSTIC CAPABILITIES
The ATC control has a computer capable of troubleshooting the entire ATC system in approximately 60 seconds. The engine must be running and at normal operating temperature during the test to provide hot coolant for the heater. During the ATC Diagnostic Test, the computer will also calibrate the Mode and Blend Door actuators, for the particular Heater/AC unit assembly.
CAUTION: Do not remove the actuators from the Heater/AC unit assembly with power applied. Removal should only be done with the ignition OFF. The actuators have no mechanical stops to limit the travel. if the actuator rotates and is not connected to the unit assembly, it will become uncalibrated.
ATC Failure Codes:
The Diagnostic Test is capable of checking all electrical signals between the ATC Control Module, actuators, sensors and blower control. The Diagnostic Test will display two types of FAILURE CODES. The Failure Codes numbered 01 through 22, have been detected during the Diagnostic Test. Failure Codes numbered 23 through 28, have been detected during normal ATC operation. Failure Codes 23 through 28 would then be stored in the ATC control computer and are only being retrieved during the Diagnostic Test.