Lamp Out Indicator: Description and Operation

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


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.


NOTE: 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.