MONOVALVE Ground Connection
WARNING: This page is about a different car, the 1997 Mercedes-Benz SL500 and 1997 Mercedes-Benz SL320. However, it is still accessible from the selected car via links, so may be relevant.
Connect test cable to right connector of ACC push-button control unit. Connect wiring harness to left connector of ACC push-button control unit. Turn ignition on. Connect voltmeter negative probe to socket box terminal No. 18. Connect voltmeter positive probe to socket box terminal No. 20. Set temperature wheel to MIN. After 10 seconds, voltage should be greater than 10 volts. If voltage is not to specification, replace ACC push-button control unit.