Acc Push-Button Control Module
WARNING: This page is about a different car, the 1997 Mercedes-Benz C280 and 1997 Mercedes-Benz C230. However, it is still accessible from the selected car via links, so may be relevant.
Connect socket box and 3-connector test cable to ACC push-button control unit right connector. See Figure. Turn ignition on. Connect voltmeter negative lead to socket box terminal No. 19 and voltmeter positive lead to terminal No. 28. About 11-14 volts should be present. If voltage is not to specification, check wiring.