Mercedes Benz W203 starter problem

Mercedes Benz W203 starter problem

About 2 months ago, my Mercedes Benz W203 C180K Kompressor's starter motor started slipping when attempting to turn-over  the engine. On average the bendix drive slipped twice for every three tries. Then it progressively got worst, requiring several more attempts before it would finally engage.  My wife was at her tethered end and refused to drive the car unless I fix it. So I planed to do so the upcoming weekend, encouraging her to use the car until then.  

However, as fate would have it, I was forced to fix it much sooner than I anticipated. My wife drove into a Fish Hoek garage for fuel and when the attendant was done, she started the car but nothing happened, the starter didn't turn over, it was silent,  not even a click. After a few more attempts she gave up and phoned me to relate the above mentioned problem, so I grabbed some tools and jetted to her rescue. 

On arrival, I checked that the starter fuse was OK and  I knocked the starter relay with a screwdriver handle a few times, but without success. Then I asked her to turn the key, while I knocked the starter with a ball pane hammer a few times, but to no avail. It started to get dark so I phoned for a roll-back and had to car taken home. The following morning I started my diagnoses. 

Mercedes Benz W203 C180k SAM with its
water proof cover removed.

I suspected that the starter was faulty but wasn't willing to remove it, not until I made sure it wasn't anything else that caused the same symptoms.  So I removed the SAM cover and once again systematically checked all the fuses with a multi-meter. I even switched on the ignition and checked for voltage on either side of every fuse just to make certain I didn't get an ohms reading through some other circuit previously. It all seemed fine, all the fuses were OK. 

Next I pulled out relay the S - starter relay, removed its cover to inspect its contact to see if it wasn't burnt and checked its solenoid for continuity. It seemed fine, but I wasn't convinced that the relay per se was OK. Now since a relay is a electro-mechanical active device I needed to test it, to see if it performs as it should. A relay is just a remote switch, implying in order for it to switch, it must be remotely controlled by a voltage originating from another switch contact. In our case, when the ignition switch is turned on, it sends power to the the relay solenoid which then activates the relay.

Mercedes Benz W203 C180k Starter Relay with the
 diagram clearly visible on its cover

The diagram on the relay cover, shows where each of the terminals  connects to, but it doesn't follow international relay convention. On the diagram, the terminals are marked as 1 and 2, 3 and 5, with 3 and 5 being the physical switch, 1 and 2 being the solenoid winding. In the above image,  the pin marked 3 would normally be marked as 87 and the pin marked 5 would normally be marked as 30. Have a look at this relay. 

These pins carry the load which is normally Open-Circuit and only closes when its solenoid winding is energized.  The pin marked as 1 would normally be marked 85 and pin marked 2 would be normally marked as 86. Be that as it may, this relay was probably an after market component, even though it sports the Mercedes Benz emblem on the other side. It worked fine even though it was a fake Mercedes Benz relay.

Mercedes Benz W203 C180k starter solenoid continuity test

With my multi-meter switched to ohms, I checked the solenoid winding and as you can see, it measures .3 of an ohm. The solenoid winding is connected to the multi-meter with 2 dog clips that is connected to the multi-meter's leads. In the image below, I'm applying 12 volts to the relay solenoid with the dog clips connected to the switch and the relay activated as it should. 

Mercedes Benz W203 C180k starter relay solenoid switching test

Mercedes Benz W203 C180k SAM with the Starter relay 
and fuse in the top left hand corner

Satisfied that the fuse is OK and that the relay was working as it should, I needed to bypass the relay, thinking that the Ignition switch may not be sending the required voltage. So looking at the image below, the relay in the far left corner, sitting behind the red fuse is the starter relay, which I reinserted. Mercedes Benz agents are fully aware of the starting problems Mercedes Benz owners are experiencing with the cars. 

So they've even published a bulletin, recommending that when their techs receive a job card with Engine Not Starting / Starter Fuse Malfunctioning, that the 15A fuse F52 which may be blown on the Signal Acquisition and Actuation Module (SAM) should be ungraded to a 20A. 

This issue affects the following sub-types of the Mercedes Benz W203 chassis:- 203.040 / 203.052 / 203.054 / 203.056 / 203.061 / 203.064 / 203.065 / 203.076 / 203.081 / 203.084 / 203.087 / 203.092 / 203.261 / 203.264 / 203.281 / 203.284 / 203.740 / 203.747 / 203.764. Essentially Mercedes Benz W203 C-Class C180, C200, C230, C240, C280 and C320 year models ranging between 2000- 2008. 

Mercedes Benz W203 C180k starter relay removed
and replaced by a link between its load contacts

As can be seen in the above , I subsequently replaced the starter relay with a thick black jumper lead, now occupying the place of the stater relay connected to pins 3 and 5 of the removed relay. With this thick black jumper in place, the starter should turn if its not faulty when I turn the ignition key. Unfortunately nothing happened, though proving decisively that the starter was indeed faulty. 

So I got out the tools and removed the starter after I had checked that the started solenoid voltage was present when the ignition was turned. Due of limited space between the bell housing and the car body, I needed to joint 2 long extensions together with a swivel adapter in between for flexibility. Then added a second swivel adapter between the extension and the 15mm spline socket, all attached to a power bar to remove the two long starter bolts.

Faulty Mercedes Benz W203 C180k starter with solenoid screws undone

After removing the starter, and cleaning the grime from it, I struggled to undo the starter solenoid screws and ended up damaging the screw heads. I then resorted to an impact-driver but to no avail because the screw heads were just too damaged. I  painstakingly hammered each screw with a cold chisel and  eventually I got them loose. Luckily I had another starter from which I could salvage three screws that were in perfect nick.

Mercedes Benz W203 C180k starter completely dismantled.

Opening up the starter was quick and easy, only to reveal that two of the four brushes were completely worn down to its very last, and two dangling copper wire braids that were attached to brush graphite at some time in the not so distant past. The brush module was clogged with grime and to make any sense of what I was dealing with, I had to clean it up.  

The faulty Mercedes Benz W203 C180k brush panel fouled with grime

So out of curiosity, I cleaned up the debris to reveal the following. One of the springs were broken and slightly worn away. A small piece of one  of the brushes survived along with the brush holders, non of which were usable because the new brush panel comes as a complete unit. The fact that the brushes didn't make contact with the armature any longer was the real reason why the starter wouldn't turn-over. Besides, it very miraculously and very surprisingly continued working until its brushes were beyond end of life. Lucky me...

Disposable parts of brush panel

Brush panel backing plate with braid wires still attached

As can be seen in the image above, the brush panel still has two bits of braided wire that was once attached to brushes. Using a stick I further removed the rest of the grime out of the field coils and wiped it down with a solvent in order to restore it to its former glory. 

The Mercedes Benz W203 C180k field coils in the process of being cleaned.

Prior to this starter problem. I had the Oil Cooler replaced which you can read about in the previous blog page. I suspected that oil had dripped down onto the starter, seeped inside and mixed with the worn-off brush particles to form a sludge. Considering that the Oil cooler sits directly above the starter, there was no other reason for the thick oil-like substance that's visible on the stick above, to be inside the starter. 

The Mercedes Benz W203 C180k field coils after its been cleaned.

With the field coils all cleaned and shiny. I started the repair process by buying a new bendix and a new brush panel kit. The part numbers are as follows: Bosch part number 1006 209 801 and Bosch part number 1004 336 526 respectively. It is also clearly visible on the respective packaging.

The new Mercedes Benz C Class W203 bendix

The new Mercedes Benz W203 brush panel 
with the brushes side up.

The back side of the new 
Mercedes Benz W203 brush panel

The old bendix drive had virtually no friction or rather resistance on rotation, so comparatively it was easy to determine that it was definitely faulty. Besides it is the only item inside the starter motor that can produce the slipping sound. Surprisingly, as can be seen in the pic below, the teeth of the bendix  where it meshes with the teeth of the flywheel weren't worn off at all. 

The new Mercedes Benz W203 bendix on the shaft and the old and worn 
Mercedes Benz W203 bendix below.

Fortunately the armature wasn't damaged in the process, and a few light strokes with a piece of  emery cloth rendered the brush contacts shiny and smooth. There was no visible wear on the armature shaft either, because the bronze bushes were impregnated with oil which dripped into the starter. 

The Mercedes Benz W203 armature before cleaning 
and the solenoid after testing it for continuity.

Reassembling the starter was quick and easy because everything just slipped together. The bendix slid onto the shaft and the fulcrum slid into its guide, all of which slid into the field coils without any fuss or bother. 

The Mercedes Benz W203 bendix assembly with the fulcrum 
balancing on top of it.

Getting the new brush panel onto the armature was simple because of the disposable plastic  guide that keeps the brushes the exact distance from the armature contacts to just slip it into place, as can be seen below.

The new Mercedes Benz W203 brush panel seated onto the armature.

The disposable plastic guide just about to pop out of place

With the rear cover in place, it was time to fit the grease cover.

Mercedes Benz W203 Bendix drive assembly ready for assembly

Mercedes Benz W203 Bendix drive inserted into casing and ready for assembly

Mercedes Benz W203 starter assembled 
but in the process I chipped a piece off the casing.

Assembly complete with screws torque to correct tension

Starter fully assembled ready for testing

Starter fully assembled Mercedes Benz W203 starter ready for testing.

Earth jumper cable connected on the body of the Mercedes Benz W203 
starter  and 12V connected on the solenoid supply side.

As can be seen the battery voltage sits at 12.27 Volts prior to testing

Multi-meter connected to battery supply shows that the voltage dipped
just under  11 volts when cranked.  As can be seen the green dog clip is
 connected to the solenoid and I'm touching the other end to the  the 12V supply,

Mercedes Benz W203 starter was fitted and car started first time

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