Testing the exterior lamp failure indicator - ra54001406070x(6070)

A. Test, B. Function Model 140 

Operation no. of operation texts and work units or standard texts and flat rates

1. Testing 
   Fig 1: Identifying Exterior Lamp Failure Indicator Components

   Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

   -----Electric wiring

   WITHOUT TRAILER COUPLING
   
   

   Lighting	switch through, visual inspection.
   Faulty circuit	determine.
   Lighting	switch off.
   	NOTE: The bulbs are monitored individually. With bulbs with lower power (watt) this is displayed as fault, with higher power no fault is displayed. For diagnoses on xenon headlamps see Diagnosis Manual
   Bulbs	test.
   	Power of bulbs
   	Low beam (standard)	H 1/55W
   	Low beam (xenon)	D2R/35W
   	High beam (sedan)	H 1/55W
   	High beam (coupe)	H 7/55W
   	Fog lamps	H 3/55W
   	Side lamp/parking lamp	5 W
   	Turn signal/side lamp	21/5 W
   	Turn signal lamp	21 W
   	Stop lamp	21 W
   	Rear fog lamp/parking lamp	21/4 W
   	Rear fog lamp	21 W
   	License plate lamp (Suffitte)	5 W
   	Reverse lamp	21 W
   Bulbs in order	test wiring according to wiring diagram for open circuit or short circuit and proper contact.

   With trailer coupling (up to approx. 2/94) 

   NOTE: The combination relay N10/2 is switched over to trailer operation by a signal from the trailer detection control module N28/1. It detects trailer operation by means of an electrical measurement at the stop lamps of the trailer.

   A faulty turn signal bulb on the trailer is indicated by the turn signal indicator lamp flashing more rapidly. At the same time, the lamp failure indicator lights up.

   1. To simulate trailer operation, connect a 12-volt 21 watt bulb to terminal 54 (stop light) and terminal 31 (ground) of the trailer socket.
   2. Turn key to position "2" (ignition on).
   3. Switch on turn signal light. Flashing frequency is faster than normal and the lamp failure indicator lights up.

   With trailer coupling (as of approx. 3/94) 

   NOTE: The combination relay N10/2 is switched over to trailer operation by the trailer recognition microswitch (X58s1). This microswitch switches power to the combination relay (N10/2) when the trailer plug makes contact for recognition of trailer operation.

   A defective turn signal bulb on the trailer is indicated by the turn signal indicator lamp flashing more rapidly. Simultaneously the lamp failure indicator lights up.

   NOTE: As of 09/95 this is no longer indicated by the exterior lamps failure warning lamp.
   1. To simulate trailer operation insert a plug into the trailer socket.
2. Function 

   The following bulb functions of the exterior lighting are monitored by the lamp failure monitoring unit (N7) in the fuse and relay box and a failure indicated by the lamp failure indicator in the instrument cluster lighting up: Low beam, high beam, fog, side, tail, additional tail, license plate, stop, turn signal, rear fog and reversing light.

   NOTE: Turn signals only up to 08/95
   Fig 2: Identifying Lamp Failure Symbol

   Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

   If a bulb in any of these circuits fails, the lamp failure indicator signals the fault for as long as this light remains switched on.

   The circuits are monitored by measuring the current, except for the turn signal light. In the case of the turn signal light, the bulbs are monitored by the combination relay (up to 08/95).

   If the bulbs are in order, a positive signal (12 V) exists at the lamp monitoring unit. If a bulb fails, by contrast, a negative signal is supplied.

   The stop light and turn signal light have a fault memory. In other words, if a bulb in one of these sockets fails, the lamp failure indicator remains on until the key is turned back in the steering lock to "1" or "0".

   The fuses of the side, low beam, high beam, and tail lights are monitored additionally.

   To detect a fault, start the engine and switch on the turn signal or stop light.

   As several lights are operated simultaneously when the lighting is switched on, a visual inspection must be made to determine where the fault is located.

   If additional lights are retrofitted, e.g. auxiliary head lamps, additional stop lamps, trailer coupling etc., the lights must be connected to the fuse upstream of the lamp failure monitoring unit. The lights should be connected upstream of the monitoring unit, otherwise the lamp failure indicator will be affected or the monitoring unit damaged.

   A failure is indicated by individual measurement of all monitored bulbs. If a bulb with reduced power (wattage) is installed in a circuit, this is indicated as a fault; in the case of a higher power (wattage) no fault is indicated.