380SL (107.045) V8-3.8L (116.960) (1982)
Control Module HVAC: Technical Service Bulletins
A/C - ACC Servo Unit Testing
TO:
OUR MERCEDES-BENZ PASSENGER CAR DEALERS
DATE:
September, 1983 REF. NO. 83/37
SUBJECT:
TESTING OF AUTOMATIC CLIMATE CONTROL (ACC) SERVO UNIT
MODELS 107,116,123
Complaints that the ACC system is not functioning properly (temperature setting can not be obtained) may now be investigated using a simplified test
program and special test harness.. By measuring the resistance changes of the feedback potentiometer with an ohmmeter when the servo motor is
operating, the function of the servo unit itself can be determined. It is expected that with the use of this test harness (previously by using the ACC tester)
the servo will be verified as either faulty or functional and help eliminate unnecessary servo unit replacements.
FIGURE 1 - ACC SERVO UNIT
Preliminary Information
Requirements for a properly functioning ACC system are a clean heater core and a fully charged air conditioning system.
If necessary, the heat output (Refer to S.I. 83/8, Part B) and the A/C output (Refer to applicable microfiche, Group 83) should be checked.
FIGURE 2 - SERVO TEST HARNESS
A.
Servo Isolation Test
1.
Remove 5-pole plug from servo unit and connect test harness plug (Fig. 2) to servo.
NOTE:
Notch in plug must be matched with tab in servo.