Technical Sprinter

Technical Sprinter

Mercedes Sprinter 2007-on and VW Crafter Coolant Level Warning Problem



The later Mercedes Sprinter and Volkswagen Crafter (and probably many others) uses a round plastic header/expansion tank in the coolant system.  This nylon spherical tank houses a rather clever float level switch that not only indicates a ‘low fluid level’ but also will illuminate the warning lamp in the dash binnacle if the ‘specific gravity’ of the coolant is less than specified – indicating to the driver that all is not too well with the coolant circuit.

Mercedes Sprinter Coolant Level Sensor Problem 4

On one of the fleet Crafter vans the coolant level warning lamp had come on and the driver had reported the fact.  When I investigated the issue there was no warning light on the dash, water level was fine but it could be clearly seen that the float inside the header tank had broken up, the plastic becoming somehow brittle and breaking away from its vertical retaining slide/guide. The internal float section is not available as a separate part so a ‘used’ second hand bottle was purchased.  After disconnecting the electrical connector at the base of the sphere, it is possible using a couple of sets of brake hose clamps to remove all the rubber hoses from the bottle in situ.  Once the single torx screw has been removed from the bottle mounting foot, orientating the bottle directly down into the void beside the engine, the connected hose-work can be removed quite easily and the bottle withdrawn upward without losing almost any coolant.  What coolant remains in the expansion tank can then be decanted back into the new bottle once fitted and piped.

Mercedes Sprinter Coolant Level Sensor Problem 3

On closer inspection once the bottle was removed, it could be seen that although the float inside the expansion tank was in this case the obvious problem (the actuating magnet it transpired, had been removed from the loose float by the driver, to turn off the lamp – why do they do that!)  Further dismantling of the float switch and level sensor revealed exactly how it functioned and also highlighted a further weaknesses that could in some cases cause issue with level measurement and warning lamp activation.

Mercedes Sprinter Coolant Level Sensor Problem 5

In the base of the tank is a moulded central vertical column that forms an upright guide that the tubular float moves on. The float rides up and down this central guide tube. Beneath and fitting into this tube is the sensor device. Although moulded in a plastic holder, this sensor is actually houses a small glass tube type reed switch that is triggered by the passing float (and magnet). The contacts of the reed switch close as the float magnet descends past a predetermined point and the warning lamp is activated. As the float rises above the reed switch, the magnet no longer causes the contacts to close and they spring open, resulting in extinguishing the coolant warning lamp.  There is a small resistor across the contact terminals of the sensor (around 800 ohms – the one I measured) This I am certain enables the ECU to detect in addition to reporting the coolant level status, a disconnected plug to the sensor, as it would have four possible measured electrical ‘states’ present between the sensor terminals as measured from the ECU. (1): Reed switch contact open, 800ohms = Correct fluid level. (2): Reed switch contact closed, short = Low fluid level or weak antifreeze water mix, Warning lamp lit. (3): Open circuit = Connecting cable disconnected or cut, warning lamp lit. (4) Cable shorted together = Connecting cable linked or fused together, warning lamp lit.

Mercedes Sprinter Coolant Level Sensor Problem 1

It can be seen from further ‘distructive’ disassembly the level sensor that it is susceptible to corrosion around the resistor and wire junctions, obviously due to the service environment it which it lives.  This discovery is important as if the float inside the water tank looks in good order, it may just be that the level sensor is faulty.  Depending on how keen you are with your fault finding, you could just slot a 1k resistor across the sensor plug and see if the warning lamp extinguished.  If it does, the chances are the sensor is faulty and can simply be rotated through 90 degrees and removed from the bottle base without any draining down or tank removal. Slotting in a working sensor, turning and reconnecting its plug to fit the replacement part.

Hopefully by exploring a little deeper how the float level switch works gives you a better understanding should you ever needed to trouble shoot the circuit.  The coolant level warning lamp is extinguished on the dash as you can see below, however you may notice the engine management lamp illuminated just behind the speedo needle hub – this is due to a faulty glow-plug and is next on the list for repair!

Mercedes Sprinter Coolant Level Sensor Problem 7


Mercedes Headlamp Adjustment Repair – Most Models


Here is a quick fix that will restore your failing or ‘wobbly’ headlamp back to a working condition.  If you notice that the headlamp leveller is not working correctly and on inspection the internal reflector seems loose and ‘disconnected’ from the lamp body – it probably is!  Caused by the internal ball and socket arrangements breaking that secure the reflector to the adjustment threaded rods.

If you are lucky the ball and socket arrangement will have just popped out and you should be able to snap them back in place once you can see exactly what you are doing.  The best policy is to remove the lamp unit and work on it at the bench or table.

Usually there is only two or three fixings that hold the lamp into the vehicle body and removal is in many cases quite simple (At least on the R170 SLK we have here)

Mercedes Headlamp Repair 1

On removing the bulb access panel you should be able to see the issue.  There are three attachment points to the reflector, looking from the back of the right hand lamp there is a ball and socket on the vacuum leveller adjuster (could be electric in some models) to the lower left and two points of attachment top and bottom on the right, these are usually a cream/white nylon part, the socket of which is screwed to the rear of the reflector.  Its worth noting that if when you shake the lamp you can hear broken parts inside there is likelihood that one of the sockets has become brittle and broken.  As far as I know, even though these small plastic socket parts look to be replaceable, I have yet find a source. It would mean in most cases a replacement lamp to rectify the fault, used or otherwise its an expensive fix for an otherwise serviceable lamp.

On the R170 SLK once the indicator unit has been removed, by slotting a screwdriver down the 10mm hole at the rear of the lamp body and flexing the latch access can be made to the steel spring clips that hold the polycarbonate lens to the grey lamp body. Once these clips have been removed the lens and body can be carefully levered apart.  The front chrome surrounding lamp trim simply pulls forward and allows full access to the reflector.

Note at this point that if you touch the shiny chrome reflector with your fingers it will mark, equally if you try and rub it with a cloth, even light polishing will damage the reflector.  I have found that using a fresh pair of vinyl un-powdered gloves prevents any handling marks and is a great aid to working with the reflector parts as it prevents any damage.

Mercedes Headlamp Repair 2


Once apart the reflector pivots can be inspected, it will be clear if just pushing the unit back together will be your fix or if further intervention will be needed if you spy broken or missing parts.  In the case of the SLK lamp, one of the nylon sockets had lost one of its three retaining ears allowing the ball to spring out of place very easily.  What was required was to retain the ball and push it into contact with the two remaining ears, giving a secure and durable mounting to the broken part.

Taking a small jewellers screwdriver (app. 1mm diameter) heat it with a cigarette lighter and melt two small holes in the plastic socket, next to the point where it fixes to the reflector body with the single torx screw.  The hole position should be so that they are level with the top flat edge of the nylon ball once it is fitted to the socket.  Thread a paper clip through the two holes and enclose its free ends around the ball whilst holding everything tightly in place.  With pliers twist together the two ends, applying tension to the socket and bridging the paperclip diagonally across the top flat surface of the ball where the retaining ear is missing.

Reassemble the lamp, threading the repaired parts back together, pushing it home into the receiver of the vacuum or electrical adjuster.  If possible always move the sockets around so that the broken one ends up on the headlamp leveller as this can be snapped into place more easily on reassembly than the other attachment points.  Often the sockets are the same moulded part fitted to different points on the reflector and this allows them to be positioned so that any repaired socket is under the least supporting stress (leveller position).

Rebuild the lamp ensuring to use a light smear of clear sealer on the headlamp lens to body gasket if it looks to be leaking or allowing any dirt build up under the lens lip. Clip back all the lens fixings and refit the lamp to the vehicle.  Adjust the beam pattern to the specifications required by rotating either the up/down or left/right adjusters, be sure to make any adjustment with the instrument leveller control set to ‘0’.

Sprinter Rear Step Repair – Fabricating a Replacement


As time passes the pressed steel under step or supporting chassis beneath the Sprinters rear step plastic skin rots.  It is only relatively thin gauge steel, with most of its strength gained from its pressed shape and side wall returns – it gets fragile and flexible to tread onto, often pulling away the vertical face of the step skin from the clips in the rear valance. Once this happens it is time to repair.

Mercedes Sprinter rear foot step repair 1

On one of the courier fleet, the step had been requiring repair for a few months and just to help it on its way the driver reversed it into a bollard and creased the edge quite severely. So bad in fact that the plastic skin was removed in the impact, leaving the full horror of the rusted and now damaged rear step requiring urgent attention.

Taking a hacksaw and chisel to the existing step plate made light work of cleaning up the area, leaving the two steel supporting brackets projecting from the chassis. (Hammered straight again!)  Once the covering had been removed a section of 50mm square box section was cut to fit between the support brackets.  A further length of 50×50 was cut to fit snugly inside the rear edge of the plastic skin, ending at each side just before it takes on the radius into the corner and edges of the step moulding.  A centre line was marked onto each section to use as a datum on assembly and welding.

Mercedes Sprinter rear foot step repair 2

The edges of the chassis support brackets were cut back by 50mm to allow the new fabrication to sit where the original edge would have supported the plastic skin and to allow as good a fit as the original.  Cleaning up all areas to be welded with a grinder including the support brackets and mating edges of the two box sections, in addition to the areas where the two pieces are to be stitch welded top and bottom.

Mercedes Sprinter rear foot step repair 3

Aligning the two centre marks, tack the box sections in place ensuring that it is both, level central and flush between the chassis support brackets.  You should be able to weld the shorter box section to the supports along the top, back and at the rear corner of its section. Then clamp on the longer section, ensuring it is central, then stick weld this to the shorter box previously welded.

Mercedes Sprinter rear foot step repair 3

Once fully welded, the construction is very strong and will support a great deal of weight, certainly it does not ‘flex’ like the original used to do when entering or exiting the van.

Cleaning off the rough edges and painting if required prepares the new step tread for re-fitting of the plastic skin.  This can be slid over the new steel and secured back to the upright section of the rear valance.  If, as in the case of our step, the moulded retaining clips had been broken, large head self tapping screws were used to secure the vertical section to the rear of the vehicle.  Additionally three 8mm holes were drilled vertically through the foot-plate area of the plastic step to coincide with the new steel box section beneath. The step was secured with coach bolts and washers, tightening them securely to finish off the job.

Mercedes Sprinter rear foot step repair 5

The repaired step is in my opinion stronger than the original and hopefully will give many years good service – unless of course it is used to determine the rear extremity of the vehicle in a parking manoeuvre, where it will not be quite as ‘forgiving’ as the slightly flexing original!

Mercedes Sprinter rear foot step repair 6


Sprinter Gear Selection Cable End (Ball Joint) Replacement


From time to time we get a call from a driver saying that he can’t select any gears and the gear stick (Manual Gearbox) has gone sloppy. Quite often we direct him to sliding underneath the left side of the van and reconnecting the ball joint end back onto the gearbox selector mechanism, at least to get him home and save recovery.  Once either or both of these plastic adjustable ends wear beyond a point where they no longer ‘snap’ onto the steel balls of the selector mechanism, its time to replace them as they will let you down.

Mercedes Sprinter Gear Selector Ball Joint ( Cable End) Replacement 1

Its super simple task and will cost you about £20 plus half an hour of time to complete the job.  The Mercedes parts you need for the Sprinter up to 2006 will be two of the following: A901 268 01 43

Mercedes Sprinter Gear Selector Ball Joint ( Cable End) Replacement 2

All you need to do to install these correctly, is elevate the vehicle enough to gain access to the underside at a point on the side of the gearbox case,  just rearward of the front left wheel. Slip off the gearstick gaiter in the cab and push down the steel locating staple on the gear lever to set and lock it at its mid-position.  Now get underneath and pull/lever off the two old ball joints from their respective positions, one on top and one to the side.

Mercedes Sprinter Gear Selector Ball Joint ( Cable End) Replacement 3

Release the grip latch that traps the cable ‘ribbed rod’ end from each balljoint, this is used to adjust the effective cable length and position the gear cable in its correct position.  Once the latch is undone the end will simply pull off the ribbed rod of the cable end.  Installation of the new ends is straightforward.  Ensure the selector mechanism on the gearbox is in its neutral at rest position.  Undo the latch on each of the new balljoints and thread them onto the ribbed adjuster rod moulded onto the end of each selector cable. Use slide or pipe pliers to squeeze the new ball joints onto their respective male steel ball towers.  Align the gear mechanism to its central rest position and use the pipe pliers as before to squeeze together the latch that grips the adjustment rod.  It will click when it is in its final position and you will see that the latch clip is fully engaged on the front face of the moulded body (where the cable enters).

Mercedes Sprinter Gear Selector Ball Joint ( Cable End) Replacement 4

From the cab, withdraw the steel centring pin (Staple) from the gear selector lever ball, ensuring it latches out of the way, back into its little indent in the upper part of the moulded body.  Test gear selection.  If all is well, start the engine and road test. Further adjustment should not be necessary, however if needed, the ball joint end/cable clamps can be simply unlatched with a screwdriver, thus allowing the bar on the cable end to be slid either further in or out of the ball joint body, before re-clamping to secure the adjustment.


Cargo area lighting control modification from Sprinter cab dome light (Models to 2006)


Having a large fleet of Sprinter vehicles running on delivery routes has its problems and one reoccurring issue is the cargo area lighting being left on over the weekend and flattening the battery. Come six o’clock Monday morning the driver rings the boss to say his vehicle wont start off the lot.

The issue really is I suppose mainly that the cargo area door pin switches get damaged both through worn fold back rear door hinges and clumsy forklift loading, worn ill-fitting doors continually not helping the situation.

mercedes pin switch

What happens is each of the rear interior light unit switches gets set to middle position (off) during the day and as unloading at the depot is done in the evening the switches are moved to the permanent on position to illuminate work. Obviously this is forgotten about when the doors are shut and they drive back to the parking lot at the end of the day. The van is then locked, keys placed at the lodge and off home the driver goes – lights still on.

So how do you modify the rear interior lighting so this does not happen? Lets take a look at how the current set up works.

Each of the three rear light units can be operated separately by their own wheel control. – Central position Off. Permanently On, or On when a door is open (pin switch activation)

There are three wire terminations to the rear of the lamp assembly; these are plugged into the loom via a three pole-latching plug. To gain access to the rear of the unit and the connector, use a screwdriver to prize the right hand edge of the plastic lamp to the left and lever it out of the pocket in the steel body. Be careful as the central copper band you can see on the back of the lamp is live 12v supply and can short on the body if you do not observe some caution when taking out the lamp unit.

Once out of the body you can identify the wires into the plug by the following descriptions.

Nearest the connector plug latch you have: Brown (ground),
The middle wire: Red-Yellow (supply)
Furthest wire away from the plug latch: Brown-White (ground via pin switch)


Below is the common schematic for UK Mercedes Sprinter vans without the timed delay illumination option (most pre 2006 cargo vans)

sprinter cargo lamp modification 1

What was required was a way to indicate that the rear lamps were on behind the full bulkhead from the driver compartment, even better if all the lights in the cargo area could be isolated (switched on and off) from the cab.

sprinter cargo lamp modification 2

Investigation of the dome lamp in the cab area found that it had two lighting circuits included within. The first, left hand lamp in the dome operates like the rear cargo lights, switch positions for Off, On, or On with front cab doors open. If you were to push the slider switch to the (Book/Map Icon) this illuminates a separate lamp in the dome that is magnified with a clear lens for map reading – adapting this switch position to control all the rear cargo lights is a perfect solution as it provides manual control and a visual indication (map light) that the rear lamps are powered. Turning off the map light in the cab ensures all the rear lighting is off and not draining the battery unseen.

sprinter cargo lamp modification 3

Because all the interior lamps are fed with a constant supply to their switches, grounded by either a door opening or selecting ‘ON’ on their individual switches, lamp control can be done in two ways.

1- Switching the common live supply to all interior lighting
2- Switching the ground to supply to all interior lighting

As the live supply is common and fused through Fuse 18 (15A) any switch in this circuit would remove power from all interior lighting, including the front dome lamp. Power to the cargo lamps is split into two sections of loom running down both the left and right side of the vehicle on the mid level box section, so adding a switch to live supply here is not straight forward.

The solution is to switch the grounds to all rear cargo lighting from the front dome lamp when in the ‘map reading’ position. To achieve this you will first have to run a new common cable between all lamps that will become your cab-switched ground. This can be fed down the cab headlining to exit at the dome lamp and run to each of the rear lights in turn. It is possible to thread the wire over and inside one of the roof supports to reach the light behind the sliding door pillar.

Because of the repeated damage to the pin switches on the doors and the nature of the use of the vans for multi-drop delivery, we no longer required the lights to come on with a door open in the rear area. What was preferred was that the driver switched on the rear lights from the cab before entering. Once he got back into the cab he would turn off the lights on the dome light switch. Should he leave the lights on in the rear the front map light would be illuminated warning him to the fact.

Sprinter Dome Lamp

Modifying the connections to each the rear lamps was simple. Cut the Brown/White wires from the plug and tape the ends, this disconnects the door pin switches. Then cut the existing Brown (ground) wire a couple of inches back from the connector and tape the loom. Now connect your new common ground to the short stub of brown wire from the plug using insulated wire-crimps.

Once all three cargo lights have been modified place their wheel switches into the permanently on position. Each lamp can still individually be turned off and isolated if needed by selecting the middle or door pin position.

Within the front dome light correctly identify the map reading bulb, this festoon lamp will be held in position by two spring clips on the PCB. Identify the outermost pointing clip holding the festoon lamp and carefully solder the new common earth cable you have run from the rear compartment to this point. Be sure to solder it to the outside part of the clip to maintain a good connection of the clip to the map bulb. (See photograph above)

Having dismantled the switch and looked how the switch functions I have determined that this point gets grounded when the switch is placed in the map light position – perfect for what we require! You could if you wished check this out on your own dome light with a test meter just to confirm your configuration is identical.

Once connected, the front dome light can be clipped back into position.

We decided to replace the existing festoon bulbs with LED types. This has two benefits for us. The first is that the light from the lamps is brighter than standard bulbs and also the total current drawn is substantially less, further ensuring that there is no chance of overrating the front dome light switch.

sprinter cargo lamp modification 4

LED bulbs were fitted to the rear light units and they were tested and clipped back into place. It worked perfectly. A few moments with the driver to explain how the new lighting worked and they were pleased with the outcome. As the vehicles are parked on a secure compound at night we briefed the security guard that should he see any interior lamps showing on in the cabs after dark (that he can see from his lodge) he would turn them off. We now know that with this modification that if there is no light on in the front of the cab the cargo area is also in darkness and we are doubly assured the van will start with a healthy battery after standing a few days.

led festoon lamp Sprinter

This modification may not suit everyone’s application but for the delivery vehicles on our fleet it was well worth the one-hour investment to modify the circuit. It is also unsuitable for later models fitted with interior light delay timers, as they are more complex and controlled by an electronic module and would not lend themselves to this type of modification.