My Roomster (2015) came to me in a bad way (I'm the 5th owner, and at that the 3rd in the last year) but determined to get her back up and running. Lots of small electricals need replacing (mirror controller, hazard light button, window controller on the passenger side, 12V power) and I've done a few to success, and so I went for the rear wiper which for some reason had been completely removed- got a 2nd hand unit and went in to install.

 

Once installed I went to test- and to my surprise all of my wipers were non functional. Fuses all checked, wires checked, removed the rear motor (front still doesn't work), can't hear the relay (can you hear the wiper relay?) and a bit stumped. Frustrated by attempts at doing the "easy jobs" means I may hgave to go to a garage to get it sorted!

 

Is there a way to reset fuses if things go pear shaped? Would like some wipers!

 

 

I'm not 100% sure about this but I suspect it would have been a canbus issue. If the system doesn't recognise the "new" wiper motor on the rear, it won't work. It's my understanding that if you have to change an electric motor driven thingy, it will need recoding.   As for why it's stopped the front wipers working may well have something to do with this system too. A cheap OBD2 reader will NOT help here as they are limited to engine faults. A complete OBD reader could well allow you to reset your system fault but again, sadly, I'm not sure. Hopefully someone on here will be able to throw some more informed light on your issue.  

I'm keen to know if my observations are on the right track too. I'm happy to be corrected if I'm wrong here ....

Edited 29 January, 20251 yr by Maxiboyo
A few letters missing

5 hours ago, Maxiboyo said:

It's my understanding that if you have to change an electric motor driven thingy, it will need recoding. 

 

Not true of the rear wiper motor which does indeed contain a canbus node however........................

 

Edited, this is wrong, my guardian angel has once again enlightened me, the Roomster uses the simpler Fabia system

 

6 hours ago, SE26Roomsterfg said:

so I went for the rear wiper which for some reason had been completely removed- got a 2nd hand unit and went in to install.

 

It could be that a previous owner removed it for vanity reasons and got fed up with a no comms error code in VCDS so removed it from the Can Gateway controller installation list.

 

I would first check the cable cores in the rear door bellows, there are probably broken or fractured ones, ditto for the front passenger door electrics but check the drivers door loop first.

 

6 hours ago, SE26Roomsterfg said:

can't hear the relay (can you hear the wiper relay?)

 

No relay in the front with canbus comms, the switching is done by the canbus node in the rear wiper unit/

 

Edited, incorrect, see above.

Edited 29 January, 20251 yr by J.R.

4 hours ago, SE26Roomsterfg said:

My Roomster (2015) came to me in a bad way (I'm the 5th owner, and at that the 3rd in the last year) but determined to get her back up and running. Lots of small electricals need replacing (mirror controller, hazard light button, window controller on the passenger side, 12V power) and I've done a few to success, and so I went for the rear wiper which for some reason had been completely removed- got a 2nd hand unit and went in to install.

 

Once installed I went to test- and to my surprise all of my wipers were non functional. Fuses all checked, wires checked, removed the rear motor (front still doesn't work), can't hear the relay (can you hear the wiper relay?) and a bit stumped. Frustrated by attempts at doing the "easy jobs" means I may hgave to go to a garage to get it sorted!

 

Is there a way to reset fuses if things go pear shaped? Would like some wipers!

 

 

 

Did you check cabin fuse 10, middle row of miniblades, second in from the end?

Neither the rear nor the front wiper motor has any connection to the CAN bus.

Edited 29 January, 20251 yr by Breezy_Pete

24 minutes ago, Breezy_Pete said:

Did you check cabin fuse 10, middle row of miniblades, second in from the end?

Ok! We have lift off atleast for the front wipers. Phew. Thanks you @Breezy_Pete. 

any idea which it would be for the rear of it is in fact a missing fuse? 

Fuse 26, 10 Amp standard blade fuse.

Bottom row (of full size fuses) second from right.

Edited 29 January, 20251 yr by Breezy_Pete
Enhanced description

6 minutes ago, Breezy_Pete said:

Fuse 26, 10 Amp standard blade fuse.

Bottom row second from right.

It was already in… ok but that’s atleast good to know it’s not a general issue for both wipers. I was replacing some fuses yesterday according to the manual I have  so moved some stuff around to fit so it explains have of it atleast. Now onto figure out why the rear wiper isn’t happy. Thanks Pal! 

Genuine or pattern replacement wiper motor?

Should be an ignition switched 12V on one of the four connector pins with something like a black/violet wire (from that fuse 26), then a brown earth wire on one of the other pins.

Last two wires will go between 0 and 12V depending on stalk command inputs.

Edited 29 January, 20251 yr by Breezy_Pete

Does the wash function work on front screen?

10 minutes ago, Breezy_Pete said:

Does the wash function work on front screen?

Yes! Actually works on front and back (back is missing the director- but the water is getting there). 
 

11 minutes ago, Breezy_Pete said:

Genuine or pattern replacement wiper motor?

Should be an ignition switched 12V on one of the four connector pins with something like a black/violet wire (from that fuse 26), then a brown earth wire on one of the other pins.

Last two wires will go between 0 and 12V depending on stalk command inputs.

Genuine but 2nd hand motor, am assuming that the problem is lying elsewhere as it was just purchased but obviously can’t rule it out. 

 

I don't (yet) have a multimeter to check things but this is super helpful- do I check this whilst the motor is operational? 

 

Measure for the ignition switched feed between the relevant connector pin and local earth pin when ignition is on,  no need for any stalk action.

You have just proved the intactness of the other two wires between BCM and washer reservoir because they power the washer pump (front wash with polarity one way, rear wash with it the other way).

Those same two wires tee off from the BCM to tell the rear wiper to either do the wash/wipe sequence or the intermittent wiping, depending on stalk position.

One may be broken between BCM and tailgate, I guess. Measure each relative to the brown earth wire, while someone tries the various stalk positions. 

If one of them never goes to 12V, it's likely to be broken.

1 hour ago, Breezy_Pete said:

Neither the rear nor the front wiper motor has any connection to the CAN bus.

 

Thanks, it was a 50/50 guess on my part whether the rear wiper system followed the Octavia or Fabia platform architecture.

 

The simpler Fabia system is far easier to faultfind, I will edit my previous erroneous posting.

I've yet to see a circuit diagram for a rear wiper system on a Skoda that is CAN controlled. 

I don't look at very recent models much, maybe there are some.

My 2006 Octavia and 2015 Yeti both are, they are of course the same platform, I had assumed that anything newer with any sort of functionality would remain with the Can comms type, I can understand a basic model like the Fabia and Roomster having a simple system, its with them that I usually make a wrong assumption.

There is CAN comms in all those cars you mention, but the rear wiper isn't connected to the bus. I promise. Not sure why you believe it is.

 

Show me some evidence that it is, if you believe I'm wrong.

 

Happy to show you circuits showing how it isn't,  but fairly sure I've done so a few times before now.

Edited 29 January, 20251 yr by Breezy_Pete
Clarity

No I always defer to your knowledge, my belief is from repairing too many times the rear wiper on the MK2 Octavia, initially I could not work out what the wiring was to fault find it, then I deduced it was Canbus, one large 12v conductor, one large ground conductor and a twisted pair.

 

You could not hot wire the thing putting 12v across the 2 large conductors you had to strip the casing and jump the 12v to the motor winding output of the PCB.

 

I'm pretty sure there was a resistance across the 2 data terminals which I took to be a termination (end of line) resistor.

 

Maybe through your portal you can pull up a wiring diagram for the 2006 Octavia 1.9PD Elegance.

 

I believe the Yeti is the same but only through observing the same cabling when I removed the tailgate trim to fit a reversing camera, in fact I recall now I tapped into the 12v supply and ground of the rear wiper motor to power it, it had the unintended consequence of lighting up the LEDS for reversing all the time the vehicle was driven so I cut through the track to them to disable them, they were daylight white not IR and shouted "nick me - nick me!" the feeble reversing lights give enough illumination for the camera at night when it switches to B&W mode.

2 hours ago, Breezy_Pete said:

Happy to show you circuits showing how it isn't,  but fairly sure I've done so a few times before now.

 

I don't think we have had this conversation before other than you probably correcting me in regard to Fabias, an incorrect assumption that I often make.

A couple of examples, Octy mk2 and Yeti. You participated in both. It's not a Fabia thing.

 

Rear wiper stopped working - Skoda Octavia Mk2 (2004 - 2013) - BRISKODA

 

2010 yeti rear wiper - Skoda Yeti - BRISKODA

 

I looked up mk4 Octavia as a very recent Skoda, just for interest, same circuit again, seems pretty universal. 

 

None of the wires in any of the V12/rear wiper circuits I've seen thus far are labelled CANH or CANL, as CAN wires always are in these diagrams.

 

Anyone know of a Skoda where there is such CAN wiring to a rear wiper motor?

 

If your rear wiper is a CAN node, you should see it on a VCDS autoscan, I would have thought. Got an example?

I have read through the first of the links and refreshed my memory, I have no recollection of that it maybe it was the post surgery painkillers.

 

Not Canbus, not Linbus  they give commands to the rear motor but we dont at present know how, as you say the motor only needs a start signal (removed to stop after self park) the other could be intermittent as I think it is a fixed delay and does not vary according to how the front delay is set.

 

If I dont forget I will look at the gateway installation list next time I use VCDS but from what you have said and the diagram I dont think I am going to find a can node for the rear wiper other than in my imagination.

 

My apologies for not recalling the learning that you gave me in the past, I had very strong painkillers last April time (I cant even recall the date!) when I broke my back and I have a memory blank of several weeks, my diary and bank statements show that I returned to Picardie during the recovery period but I have absolutely no recollection of the visit.

 

Aha!!!! its fallen into place now, I was hospitalised with Cellulitus Orbitale shortly after the 2023 cataract surgery (mentioned in the first thread) it was like Sepsis but even worse, I was away with the fairies for a week or so in the hospital (and also blind) and would have been on very strong painkillers afterwards when I was not allowed home but had to stay with friends.

I think I need to have a tinker with my 9n Polo, currently off the road, to measure those WW and INT connections during the action to see directly what occurs. 

I was going to suggest you might like watching this guys Youtube channel, its a garage that seem to specialise in the diagnosis of car electrical problems, I have learned a lot from them, the 2 characters might grate a little, they are a bit 'deese dem and doze" and make a horlicks of the past tense but the boss man really knows his stuff and explains the process really well using the wiring diagrams on a large screen.

 

I just looked to find a link and lo and behold this video includes a Polo with a wiper problem amongst others:

 

 

I watched another of his recently when he was teaching the apprentice the logical steps to go through with a non starting diesel engine when you have no information to go on (car bought non running from an auction) I learned a hell of a lot especially regarding cranking airflow through a broken EGR, it was like being a fly on the wall while someone else was being taught.