MB Sprinter - Additional driving lamp

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Updated - April 12, 2025

Additional spotlights provide more light. You can have them fitted by the workshop and are relieved of all worries regarding installation and wiring, but also significantly relieved in financial terms.

How you can tackle the matter yourself and solve the project on your own is explained below.

Problems

The first step is to select the right headlight(s) that meet the country-specific requirements and to create the conditions for mechanical attachment or installation. This is certainly the least of the challenges at first.

It now becomes more difficult if, as is usually the case, you want to switch these additional remote headlights using the "headlight flasher" lever on the steering column. Because now you have to find "the" cable that is responsible for this. Without a wiring diagram, you're in a bad position.

The friendly guy turns out to be uncooperative, "... we are not allowed to give it out", he says when asked personally. It was to be expected, but trial and error makes perfect sense.

Dr. G was equally non-communicative when it came to specific circuit diagrams. But one Document served to shed light on the basic functionalities of electrical units.
One would have expected that there would be fuses somewhere for the standard high beam headlights that could be used to activate a relay for the additional high beam headlight(s). However, there are electronics at work here that are BSG or SAM (signal acquisition and control module) and uses the permanently programmed current flow of individual loads to decide whether everything is OK or whether there is a fault and subsequently switches off the power supply until the fault has been rectified.

Unfortunately, you won't find this module in the circuit diagram collection linked above. However, quite a few conversion enthusiasts have already faced this problem and some knowledgeable people have shared the secret, e.g. in the Sprinter Forum. There you will find a description of the connections on the SAM. The one you are looking for is the connection of the white-red cable at the slot mentioned at the beginning of the previously linked document X7the last plug seen from below.

Removing the cladding

To access the plug, it is helpful to remove the two screws on the edge of the lower trim panel at knee height on the driver's side, as well as those on the left trim panel below the air outlet. Both panels can then be pulled off downwards at the front.

The next step is to remove the three screws from the access cover to the left of the driver's seat so that the L-shaped plastic cover can be removed. This clears the way to remove the floor mats including the underlay.

The last requirement is to release the holder of the lever for opening the hood by loosening the two screws in order to be able to remove the side panel and gain more or less unhindered access to the aforementioned connector. X7 to obtain.

The plug release is released by pressing in the two small plastic latches at the top and bottom and removing the plug.

After the plug has been moved behind the other wiring harnesses towards the footwell, the white-red cable can be cut about 5 cm from the plug, the ends stripped by about 10 mm and reconnected using a WAGO terminal. Another cable with an identical cross-section is connected to the WAGO terminal pointing away from the plug, parallel to the existing white-red cable. This now serves as a signal line for the subsequent circuit to activate the additional high beam light(s).

Additional relay board and power relay

Now that it is known that the SAM If the current flowing to the load is checked, there should be no irritation, e.g. due to the power demanded by a power relay to be switched.
Here, the control of an optocoupler, which is satisfied with a few mA and is not important for the current measurement of the SAM falls.

Finished Relay circuits can be configured with regard to the polarity of the activation signal (positive or negative rising edge) by means of a jumper and allow the electrically isolated activation of a relay, which in turn activates a Power relay switches.
If even the most powerful auxiliary lights draw less than 20 A, it makes sense to install relays with a nominal switching capacity of around 100 A. On the one hand, the current ratings are rarely based on continuous loads but rather peak loads for just a few seconds, and on the other hand, sticking contacts as a result of overheating are no fun if the light can be switched on but not off.

Connection of relay board and power relay

The relay circuit board and power relay are housed under the driver's seat, the power relay is attached to one of the two holes in the rear panel of the seat console using the lug.

The opto-coupler relay board is connected via ignition positive (tapped from the upper left fuse strip accessible from the outside, one of the three thicker cables under the driver's seat) to the connection DC+ and 12 V DC negative (ground screw connection under the advanced driver's seat at the rear right) to DC-. To the screw terminal IN the signal line is connected. As the control signal is DC+, the jumper must be set to H (high) position.

Ignition plus makes sense because, on the one hand, the high beam only works when the ignition is switched on, so only then is the signal line live, and on the other hand, this prevents the starter battery from being discharged unintentionally.
If the auxiliary headlamp is to be operated independently of the ignition, one of the thicker red cables to the right of the fuse strip must be selected instead of one of the three thicker cables carrying only ignition positive.
An additional switch must also be used to supply relay contact 85 with continuous plus instead of ignition plus in order to activate the power supply to the auxiliary headlights.

The middle relay contact (COM) is used with DC+ and conducts 12 V DC plus to the coil contact when switched on. 85 continue. Contact us 86 is connected to 12 V DC minus (ground). Contact 87 is connected to the plus wire of the auxiliary spotlight. Contact 30 leads to a fuse according to the bulb manufacturer's data sheet, whose free contact NO of the relay board is supplied with 12 V DC, also tapped at the ignition positive.

All cables should be secured with cable ties to prevent accidental slippage.

Functional test

If the high beam lever is now actuated, the optocoupler switches on the relay of the relay circuit board, which energizes the coil of the downstream power relay, conducts the current flow to the auxiliary high beam light and switches it on.

If everything works as desired, the cladding, etc. can be fitted in the reverse order to removal.