Trailer towing*
Fitting the ball coupling
Before you can tow a trailer with your vehicle, you must fit the ball coupling.
There is a key for the ball coupling.
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Make a note of the key number.
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You can use this number to obtain a replacement key from a Mercedes-Benz Service Centre.
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 | Risk of injury |
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If the ball coupling does not engage correctly when it is mounted, the vehicle/trailer combination is not secured and the trailer could come loose. This could cause an accident. Fit the ball coupling carefully and make sure that it engages in position correctly.
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The removable ball coupling is located in the stowage well under the boot floor more.
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 | Protective cap |
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 | Key |
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The key remains inserted when you remove the ball coupling.
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 | Ball coupling recess |
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Pull the handwheel away from the ball coupling to the right and turn it clockwise until it engages.
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The white dot on the ball coupling is aligned with the red area on the handwheel.
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Insert the ball coupling vertically from below in the direction of the arrow into the ball coupling recess at the mark on bumper until it engages.
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 | Green area on the handwheel |
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The handwheel turns so that green area on the handwheel is aligned with white dot on the ball coupling.
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Turn the key to the stop in the direction of the arrow (lock).
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Remove the key.
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Press protective cap onto the lock.
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| Risk of accident |
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The ball coupling is only securely mounted when the green area on the handwheel is aligned with the white dot on the ball coupling and the key can be removed. If the ball coupling is not securely mounted it may come loose.
The ball coupling must be locked and the key removed when towing a trailer. This is the only way to guarantee that the ball coupling is secured and cannot come loose while the vehicle is in motion. If the ball coupling cannot be locked and the key cannot be removed, remove the ball coupling and clean it.
If the ball coupling can still not be fitted (locked) once it has been cleaned, remove the ball coupling. The trailer tow hitch must not then be used to tow a trailer as safe operation is not guaranteed.
Have the entire trailer tow hitch checked at a qualified specialist workshop. Mercedes-Benz recommends that you use a Mercedes-Benz Service Centre for this purpose. In particular, work relevant to safety or on safety-related systems must be carried out at a qualified specialist workshop.
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Fold down socket .
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Notes on towing a trailer
| Risk of accident |
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When reversing the vehicle towards the trailer, make sure there is nobody between the trailer and the vehicle.
Couple and uncouple the trailer carefully. If you do not couple the trailer to the towing vehicle correctly, the trailer could become detached.
Make sure that the following values are not exceeded:
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The permitted trailer drawbar noseweight
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The permitted trailer load
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The permitted rear axle load of the towing vehicle
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The maximum permissible gross vehicle weight of both the towing vehicle and the trailer
You will find the applicable permissible values which must not be exceeded in the vehicle documents.
You will find the values approved by the manufacturer on the vehicle identification plates and those for the towing vehicle in the “Technical data” section.
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You will find installation dimensions and loads in the "Technical data" section more.
The maximum permissible trailer drawbar noseweight on the ball coupling is 75 kg. However, the weight must not exceed the figure given on the trailer tow hitch and trailer identification plates. The lowest weight applies.
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Use a noseweight as close as possible to the maximum permissible noseweight. Do not use a noseweight of less than 50 kg, otherwise the trailer may come loose.
Bear in mind that the payload and the rear axle load are reduced by the actual noseweight.
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The height of the ball coupling changes with the load of the vehicle. If necessary, you should use a trailer with a height-adjustable drawbar.
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Coupling up a trailer
| Risk of injury |
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Do not connect a trailer with an engaged overrun brake. Otherwise your hand could become entrapped between the bumper and drawbar.
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Do not uncouple a trailer with overrun brake between the bumper and drawbar, otherwise your vehicle could be damaged by the spring action of the overrun brake.
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Position the trailer level behind the vehicle.
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Couple up the trailer.
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Establish the electrical connection between the vehicle and the trailer.
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Driving tips
In Germany, the maximum permitted speed for vehicle/trailer combinations is 80 km/h.
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A maximum speed of
80 km/h should not be exceeded, even in countries where higher speeds are permitted for vehicle/trailer combinations.
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When towing a trailer, your vehicle's handling characteristics will be different in comparison to when driving without a trailer.
The vehicle/trailer combination:
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is heavier
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is restricted in its acceleration and gradient climbing capability
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has an increased braking distance
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is affected more by strong crosswinds
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demands more sensitive steering
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consumes more fuel
On long and steep downhill gradients, you must shift to a lower gear or, on vehicles with automatic transmission*, select shift range 1, 2 or 3 in good time.
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This also applies if you have activated cruise control, Distronic* or Speedtronic.
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This uses the braking effect of the engine and you will not have to brake to such an extent to maintain the same speed. This relieves the load on the brake system and prevents the brakes from overheating and wearing too quickly. If you need additional braking, depress the brake pedal repeatedly rather than continuously.
| Risk of accident |
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Never depress the brake pedal continuously while the vehicle is in motion, e.g. never cause the brakes to rub by applying constant slight pedal pressure. This causes the brake system to overheat, increases the braking distance and can lead to the brakes failing completely.
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Driving tips
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Maintain a greater distance from the vehicle in front than when driving without a trailer.
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Avoid braking abruptly. If possible, brake gently at first to allow the trailer to run on. Then increase the braking force rapidly.
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The values given for gradient-climbing capabilities from a standstill refer to sea level. When driving in mountainous areas, note that the power output of the engine and with it its gradient climbing capability decrease with increasing altitude.
If the trailer swings from side to side:
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Do not accelerate.
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Do not counter-steer.
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Brake if necessary.
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| Risk of accident |
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On no account should you attempt to draw the vehicle/trailer combination out by increasing speed.
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Removing the ball coupling
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Fold up the socket.
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Pull the protective cap off the lock in the handwheel.
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Use the key to unlock the lock in the handwheel.
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Hold the ball coupling. Pull the handwheel away from the ball coupling and turn it clockwise until it engages.
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The red area on the handwheel is aligned with the white dot on the ball coupling.
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Pull out the ball coupling downwards.
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Clean the ball coupling if it is dirty.
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Press the protective cap into the ball coupling recess until it engages.
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Make sure that the protective cap is firmly seated.
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Storing the ball coupling
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Place the ball coupling with its key inserted in the ball coupling stowage well in the stowage well under the boot floor.
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| Risk of accident |
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Do not carry the ball coupling in the vehicle interior if it is not secured.
Otherwise, you and others could be injured by the ball coupling being thrown around if you:
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Trailer power supply
The trailer socket of your vehicle is equipped at the factory with a permanent power supply.
The permanent power supply is supplied via trailer socket pin 9.
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You can connect accessories with a maximum power consumption of 240 watts to the permanent power supply.
You must not charge a trailer battery using the power supply.
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You can obtain further information about installing the trailer electrics from a qualified specialist workshop, e.g. a Mercedes-Benz Service Centre.
Trailer with 7-pin connector
If your trailer has a 7-pin connector, you can connect it to the 13-pin socket on the ball coupling using an adapter or, if necessary, an adapter cable. Both of these can be obtained at a qualified specialist workshop, e.g. at a Mercedes-Benz Service Centre.
Fitting the adapter
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Open the socket cover.
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Insert the connector with lug into groove on the socket and turn the connector clockwise to the stop.
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Make the cover engage.
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If you are using an adapter cable, secure the cable to the trailer with cable ties.
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Make sure that there is sufficient cable play so that the cable cannot become detached when cornering.
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