Perform Function Test Of Ball Neck And Light Signals On Trailer Hitch Socket - AN31.10-P-0008-01LWG

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Model 253.3/9

Connect light strip (1) or similar test equipment to trailer socket.
Switch on left turn signal indicator, right turn signal indicator and hazard warning system one after the other and check for proper operation.
Simulate failure of the left or right direction indicator lamp.
The flashing frequency of the indicator lamp in the instrument cluster must double.
Switch on standing lights and check for proper operation.
Engage reverse gear and check backup lamps for proper operation.
Press brake pedal and check brake lamp for proper operation.
Switch on rear fog lamp and check for proper operation.
The rear fog lamp on the vehicle must not light up.
Simulate failure of rear fog lamp on trailer.
The rear fog lamp on the vehicle must light up.
Check the constant voltage connection (terminal 30) at the trailer socket.

Courtesy of MERCEDES-BENZ USA
1. 10.1 On vehicles with fully electric swing-away ball neck Check whether ball neck folds in and out properly.
  See the vehicle operator's manual for the exact operation steps.
2. 10.2 On vehicles with removable ball neck
  Check whether the ball neck can be installed and removed.
  
  See the vehicle operator's manual for the exact operation steps.