Ive removed it and fitted an aftermarket unit which doesnt work. However,If I power the aftermarket unit on the bench using just 2 of the four terminalsit works. If I power the oem unit on the bench in the same way it doesnt work. However if i bench power the two very small exposed terminals at the actual motor and not through the plug, the oem unit does work. Is there a controll module somewhere as I see four wires in the plug but only two are needed to get the motor to turn?

Confused ....

3 hours ago, ecr7 said:

Ive removed it and fitted an aftermarket unit which doesnt work. However,If I power the aftermarket unit on the bench using just 2 of the four terminalsit works. If I power the oem unit on the bench in the same way it doesnt work. However if i bench power the two very small exposed terminals at the actual motor and not through the plug, the oem unit does work. Is there a controll module somewhere as I see four wires in the plug but only two are needed to get the motor to turn?

Confused ....

The other two wiper connections will be for the park position switch (allowing the wiper arm to return to park position at switch off) I'd suggest checking continuity of all connections on the connector plug.

Thanks for your reply, its appreciated.

The car loom continuity checks out ok but sadly theres no way of back probing the motor as all the connections are moulded in. I guess Ill have to buy an OEM motor and try that

Im wondering if its the column switch thats at fault. Can this be easily checked?

I assume that you have tested the fuse?

You could try using a pin (to connect test meter) piercing the wire insulation near the connector to test for 12 volts, this would also serve to prove the column switch.

Yes there is a control unit, it is inside the wiper motor assembly, it is a Canbus controller, the motor is not switched in the way you think it is which explains the bench test enigma.

 

The wiper column switch switches a small control current from the relevant inputs of the body control module/comfort control module or whatever yours is called, this then sends data signals via Canbus to the wiper motor controller (and others that have an interest) and the switching is done on the circuit board of the wiper motor unit. It will have 4 wires, a large core live and neutral and a smaller twisted pair for the Canbus data line, if there are others then its because that node activates other equipment in the vicinity like high level brake light, door lock etc.

 

Its all about reducing the switching current of switches and control buttons etc and reducing to a minimum current carrying conductors running around the vehicle relying on local controller nodes.

 

You cannot test the operation of the motor in the way you would have done on previous vehicles, it requires a complete reset or rethink of your learned diagnostic experience and that goes for pretty much all the equipment on the Octavia 2 and later vehicles, the rear wiper motor is a good one to cut your teeth on and learn from, it was what opened my eyes.

 

With VCDS and an understanding of how the canbus controllers work faultfinding, diagnosis and testing becomes very easy.

Pin 1 is earth, brown wire.

Pin 4 is a switched 12V, black/violet wire.

Pin 2 is labelled INT (intermittent operation?) on circuit diagrams, fed by a green/red wire.

Pin 3 is labelled WW (wash/wipe?), a green white wire.

These two wires originate from the BCM, and also connect to the terminals of the washer reservoir pump.

 

Thanks for all the information guys.As I don’t have any canbus knowlege or test equipment, It looks like the best course of action is to fit an oem motor rather than an aftermarket unit.

Thanks again👍

@ecr7 I don't think there is any such involvement with CAN. CAN wiring is always labelled as such on wiring diagrams, and none of these 4 wires are.

It's also implausible that the only connections to the washer pump would be CAN wiring.

I've proposed this before but will reiterate here in the hope that someone may confirm, but this is how I think it must work, given the connectivity.

 

Ignition switched power and earth - power up the minimal electrics/electronics inside the rear motor assembly, ready for input controlled action.

 

WW input taken to 12V while INT is at 0V = wash wipe cycle initiated (washer pump will run in appropriate direction for rear wash while these inputs are so polarised).

 

INT input taken to 12V and simultaneously WW taken to 12V, intermittent wiping function initiated  and continues until both are taken back to 0V. (Washer pump won't run because both connections to it are at 12V).

 

I can't see how else it can work, but would be happy to be shown if someone knows different.

HI ECR7,

                  and all responding to this thread. I too have this same problem but have still not worked out the problem of the wiper not working. if you dont mind I would like to follow this thread just in case anyone finds the fault............................kind regards

Watch this space 🤣

I agree with what you say Pete from the info you have gleaned from the wiring diagram however having repaired the one on my 2006 MK2 Octavia a couple of times the only way I could get the motor to turn under bench test was by directly powering the windings, it also had large 12v and ground wires and the other two were twisted pair so my conclusion then and now was that it was a canbus node and I think it was even the last one with the EOL termination resistor.

 

I can see a couple of things in your hypothesis that are worth reflecting on:

 

An "intermittent function initiated" being a pull up to 12v does not take into account the differing pause times selected by the stalk switch, perhaps its a coded signal.

 

"Wash wipe cycle initiated" The rear wiper does not control the washer pump and a wash wipe cycle is simply run at X speed for as long as commanded, why would that be a different input to the one for continuous wiper operation until input removed?

 

What about the various wiper speeds and the tear wipe programmed function?

 

I'm pretty sure on my MK2 all this was handled by the body control module and the relevant commands sent to the rear wiper module and the washer pump controlled by sending 12v or reversed polarity 12v to it.

 

I could confirm by looking at the Gateway installation list on my Yeti, if there is nothing resembling the rear wiper motor then I was wrong.

 

For sure the wiper motor and a lot of other equipment on the vehicle cannot be faultfound or tested in the traditional way of hotwiring things.

 

I too would really like to know exactly how it works because its only a matter of time before the one on the Yeti plays up, the only saving grace being the lack of rain where I now live!

Does the rear wiper have more than one speed, or adjustable pauses when functioning intermittently? Fronts, yes, but rear?

Fronts yes

rear no….

Ooops, silly me! Brain fade again!

 

It does pause the intermittent wiping when you stop at traffic lights (or anywhere really) which is kind of neat.

 

Plus the dribble wipe but both of these are commanded by the Body/Comfort control module.

Edited 24 August, 20241 yr by J.R.

Given that its functionality seems to be simply to operate when commanded by the Body/Comfort Control module and to self park there would be no need for it to be a Canbus Node yet I'm sure that was the case on my MK2 Octavia and it came as a surprise to me.

Does it? I’ve never noticed …

The pause while at lights?

 

It took me ages to twig it was happening as I rarely am driving in bad weather in urban areas and you dont really notice the absence of something in conditions where it is not needed, it was on moving off again that I realised it may well be something selected by long coding.

I recently fixed mine by prying the motor tabs open and removing the armature as the brushes still had some meat left I cleaned up the com’ and brushes re assembled drop of oil in the bearings and rebent the tags - it worked,       when dismantling make a note of the “ rack to pinion position “ this will ensure the arm parks back in its original position . Also check the spindle isn’t binding in its bushing. 

Thanks for the reply but I don’t think that’s my problem. The motor operates ok when 12v is applied directly to the very small external contacts…

So, I gave up and took it to an autoelectrician. I told them that I had tried 2 new motors without sucess and they were puzzled. The wiring to the motor and the switching checked out perfectly so they tried a new (aftermarket) motor. Bingo, all works. As unlikely as it sounds I must have had 2 duff motors (or wrong models perhaps?).

They confirmed that there is circuitry in the unit that can fail and this will prevent the unit working even though 12v applied directly to the motor and not via the plug operates the motor.