Friday, December 3, 2021

Exercising the right to repair - DYI fixing a Volkswagen Polo 6C windscreen wiper stalk (no parts replaced)

I just went on holidays and did a road trip. Because Murphy is always lurking, I was taken by surprise with runaway window wipers. No matter what position of the wiper stalk, these would run in intermittent mode all the time, as long as the ignition would be on.

In order to minimize the wear on the motor and brushes everytime it would not be raining, all I could do was to remove the fuse that protects the windscreen wiper circuit.

As I did not know which fuse could be removed for this effect, I had to do some searching (fortunately had good cellular coverage during the journey) in order to find some information on the fuses for this car model. Unlike olders cars where things as simple as fuses are normally well documented to help users autonomously perform replacements or do some basic troubleshooting, these newer generations of vehicles are totally opaque in respect to that. The idea is that users should be kept away from doing any kind of technical intervention no matter how simple.

With some luck I found a pretty decent guide containing a detailed indication of each fuse from the two main fuse boxes that can be found in this car model:

That allowed me to determine that Fuse 8 from the engine bay fuse box was the one that had to be removed in order to disable the windshield wiper.

Whenever it would start raining, I would have to open the hood and put the fuse back in place.

As soon as I got back from the trip, I had to take care of a permanent repair. I did a more careful analysis, including the use of the Obdeleven tool to monitor the state of the wiper upon testing the stalk in each of the positions, and became convinced that the problem was most likely related to electrical contacts in the switch itself.

Did some research, and quickly "guesstimated" that sending the car to the dealership for repair would certainly not come cheap. The OEM part is a single block that contains both the wiper stalk and the turn signal/high beam stalk. More specifically, the part number is 6C0953513 / 6C0953501. Searching online I could find prices between 50 and 100 Euros for the part used or advertised as new.

From previous experience, and knowing how much VW dealerships usually charge for repairs (a sum of material costs, comissions over the material costs and labour, VAT and what not), likely I would have to shell out no less than a few hundred Euros no matter what.

As such, and because my vehicle is no longer covered by the warranty, I considered that I didn't have much to loose in attempting to fix what I suspected it would be relatively simple. In the worst case I would have to take the car for repair anyway.

And so I went. The first challenge that I faced, was the fact that the part cannot be directly removed from the steering column. Because it forms a ring around the latter, there is no other option but to remove the steering wheel and the clockspring (more on that one later) in order to finally be able to remove this steering column switch.

By watching some videos of other users doing a similar operation on other VW Polo and Golf vehicles, I was able to obtain relevant indications on what had to be done in this case.

For starting it is best to have the wheels straight and the steering wheel at 0º (as when going in the forward direction with the vehicle).

The first thing that is necessary to do is to remove the two plastic shells that cover the steering column. For that effect there is a Torx screw in the bottom shell that needs to be removed first:

In order to facilitate the removal of the shells it is best to reajust the steering wheel and keep the adjustment lever in the unlocked (up) position.

The top shell needs to be separated in order to have access to the two remaining screws that keep the bottom shell secure. In order to do so, it is best to use a plastic tool to help separate and detach the top shell (a regular screwdriver may damage the plastic).

Once the shells are removed, the back of the steering wheel becomes more accessible. With this we enter a more delicate step of the operation which requires extra attention.

Because in order to remove the steering wheel we will first need to remove the airbag, some safety precautions are necessary: while the purpose of the airbag is to save lives, if inadequately handled it can be a lethal device (1). 

As such the first thing that should be done is to disconnect the battery. Because some capacitors may still hold a charge after the battery is disconnected (normally the airbag control modules have large capacitors to allow the detonation even if the battery is disconnected during the accident), it is best to wait about 15 minutes after disconnecting the battery to ensure that no charge is present.

While removing the airbag from the steering wheel, it is important to keep a distance of about 60 cm (2 ft) from the face of the airbag in order to avoid injury in case of an accidental detonation.

In my specific steering wheel (this took me some time to figure out), the airbag is secured via a release mechanism which is kept locked via a pair of springs. These are accessible via two holes which are initially closed, only recognizable by the indentations that these form:

It is necessary to poke these holes with a screwdriver at least 6 cm long, and tilt the latter, so that its tip presses the cilindrical area of the spring towards the center of the steering wheel. In order to have proper access to these holes, the steering wheel needs to be turned 90º to the right, and then once the first one is done, turn to the other side (90º left from the center) and repeat the procedure. The springs need to be pressed sufficiently, so that the tips move away from the locking mechanism enough to release the airbag module from the steering wheel. It takes some persistence and amount of force on the screwdriver to get the module fully released. Below, the springs which keep the airbag in place:

Once the airbag module pops off, there are two connectors which need to be carefully removed. There is the larger yellow connector which attaches to the clockspring socket, and a smaller black connector which provides the connection to the steering wheel buttons. In order to remove the yellow connector, there is a white tab which needs to be pulled out in order to unlock the connector. Then it can be released by pressing and pulling it.

The black connector can be easily removed by pressing and pulling it as well.

Once the airbag is out of the way (keep it in a safe place), the screw that keeps the steering wheel in place becomes accessible. In order to remove it, a triple-square (XZN) M12 driver is required. I used one coupled to an adaptor for a ratchet wrench.

Here substancial force is required, because besides being well torqued, the screw also has thread lock on it to prevent loosening due to the vibrations.

Once the steering wheel is removed, we can see the clockspring, and here we need to be careful. In order to remove it, there are two silver screws in the top and one in the bottom.

We must make sure that the clockspring is not unwound before and after we remove it. It needs to be in the same position as it was initially, otherwise the steering will not work properly and the ribbon cable inside the clockspring will be shattered once the steering wheel is turned.

To keep it in place I put tape around it, therefore preventing accidental rotation.

In case of accidentally unwinding it, and assuming that the steering was relatively close to the center (less than a full turn), there is a window in the clockspring which allows to take a peek inside, and see where is the ribbon cable. When the position is more or less at the center, the ribbon cable is visible through the window:

In this case try to install the clockspring, respecting the turn where the ribbon cable appears in the window.

With the clockspring removed, we can finally remove the steering column switch. First the two connectors need to be detached from it:

Similarly to the airbag connector, these are also locked by a tab. Pull the tab before pressing and pulling the connectors out.

The switch block is held in place by three tabs, two in the top and one in the bottom:

These tabs need to be slightly lifted while pulling the switch block.

After these steps, the steering column switch block is finally off. I started by removing the cover on the right stalk, which is the one controlling the windshield wipers.

I immediately found that the lubricating grease on the contacts was practically black.

Assuming this to be carbon, it could well justify the defect, by the establishment of a conductive bridge between two of the contacts on the switch, causing the wiper to stay on (in the photo above I had already cleaned the grease from the bottom part of the switch).

So I first cleaned the contact pads thoroughly with isopropyl alcohol, as well as the brushes. Regarding the latter, I have removed these from the plastic housing, and retensioned the spring that is behind:

Finally, applied the silicone grease (aka dielectric grease). 

In my case I used the CX80 brand, but I guess any other equivalent grease is suitable.

I also opened the left stalker switch. While it was in better condition and I did not observe any failures, I considered a good idea to proactively do the same treatment in order to extend the life of the part. This side has a somewhat different design, with a curious set of 3 switches operated by a sliding part. 

These switches serve exclusively to engage the high beams. In spite of there being only three possible states for these lights (off, on and momentary, where the latter can be engaged also when the low beams are off), for some reason this function is implemented with 3 separate switches. Another curious aspect is that by the size of the conductors, contact pads and terminals, these switches must have substancial current handling capability. I believe it is unlikely that the current from the actual bulbs goes through these switches, because the low beams and high beams can be actuated digitally via the diagnostics port (e.g. through component tests) which I routinely do with the help of OBDEleven to test all the lights, and also it usually is not a safe and by principle a good practice to bring the high current rails all the way into the dashboard. Normally there are relays in place for keeping the high current paths short and away from ignition sources.

To help test the switches before installing in the car, I have first established the schematic diagram of each switch. This way it would be easier to test continuity in all of the possible positions.

Regarding the righ stalk (window wiper controls), I obtained the following diagram:

And for the left stalk (turn signal and high beams):

Pins 7 through 10 correspond to the high beams control, but I did not trace these (these are routed to the 3 switches I have mentioned above) because it was not too relevant to test these at the time. Pins 1 through 6 are unpopulated in the connector.

With everything cleaned, lubricated and tested, it was now time for reassembly. The first item to be inserted in the steering column is the switch block obviously.The two connectors should be attached prior to fully inserting the switch block, otherwise it might be difficult to place these afterwards.

Next, put the clockspring back in place without messing up the position:

The steering wheel can then be put back in place. Make sure it is aligned exactly with the markings present on both the steering wheel and the steering column:

Before placing the screw, do not forget to add thread lock. This is essential to ensure that the screw does not become loose later due to the normal vibrations of the steering column.

There is certainly an exact torque value for this screw in the service manual of the vehicle. Given how much force it was necessary to remove it (part of it due to the thread lock of course), I torqued it with the pressure I was able to apply using my ratchet wrench.

Finally, and again as important as during disassembly, disconnect the battery for the task that follows, also ensuring that the 60 cm distance from the airbag is respected. Again, wait 15 minutes after disconnecting the battery and before installing the airbag.

Attach the black connector to the steering wheel, and the yellow connector the to clockspring. Make sure to push the white tab down in order to lock the connector:

To attach the airbag module to the steering wheel, just press it against it until it clicks in place and is evenly fitted.

At this point the battery can be reconnected. If there was no replacement of the clockspring, and it is correctly reinstalled, no recalibration procedure should be needed. In order to make sure that the steering angle is still being correctly measured by the vehicle, I connected OBDEleven again, and checked the steering angle by doing the following:
  1. Selected the Power Steering control unit (number 44):

  2. Entered the realtime data menu:

  3. Selected the steering angle measurement (there are also other counters which display the raw angle value, we want to select this one as it provides the calculated value):

  4. Click OK. The current angle should show up in the screen:

If the steering wheel is centered, a value close to 0º should be displayed.

Regarding the wipers, a regular test of the all the functions (front and rear wipers, water spray, all the speeds and cadences) should be performed. In the scan tool, the position of the stalks can also be read and verified. For that effect:

  1. Open ODBEleven and select the Central Electronics module (number 09):

  2. Select Realtime data:

  3. Select the window wipers measurements:

  4. The realtime values should now appear:

It is a good idea to drive the car a few kilometers, test the wipers and the turn signals and check if the steering and the horn are fully functional. After the drive is completed, run a scan on the diagnostic tool to see if new errors show up.

Overall, this serves to show that the simpler repairs can often be compressed to a very reduced cost assuming the user has the skills, interest and time for that effect. In my case (several of the required tools I had beforehand) the material cost boiled down to:
  • Set of XZN tool bits (including the required M12) - 18 €
  • Tube of silicone lubricant grease (CX8 Silicone grease 40 gr) - 6 €
  • Thread lock (Pattex Nural 50) - 6 €
The other tools and consumables that are required, but in my case I didn't have to spend extra money on these, were namely:
  • Isopropyl alcohol;
  • Screwdriver;
  • Racket wrench and hexagonal keys (for disconnecting the battery and to couple with the XZN bit);
  • Torx screwdrivers;
  • Plastic tool (for separating the steering column shells);
  • OBDEleven dongle and application.

1 - In order to inflate in a very short amount of time (as required during the violent and fast nature of a collision) an apropriate gas generator substance needs to be detonated. Traditionally, sodium azide (NaN3) was used by the airbag industry for this effect, but given its toxicity, it have been gradually replaced by other equally effective chemicals (e.g. nitroguanidine or guanidine nitrate). These gas generator substances have characteristics which can easily classify these as high explosives. In the case of an airbag, we are basically dealing with a carefully engineered quantity of a high explosive, which during its detonation will generate just enough gas to quickly (a few tens of milliseconds) inflate a fabric bag. This bag also deflates quickly in order to provide the correct amount of compliance when the passenger hits it, and as such provide the life saving cushioning that is needed. During inflation, an object  standing within the radius that will be occupied by the airbag, will experience forces that are very similar to a blast. As such, when handling an airbag and in case of risk of an accidental detonation (e.g. when dealing with electrical connections related to the airbag), it is important to keep a safe distance from it - at least 60 cm. When the airbag is no longer attached to the car, it is potentially more dangerous as it can behave as a very powerful projectile.

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