This is my second posting about my rear demister on my Skoda Fabia Mk3. My rear demister hasn’t been working for some time and I’ve not been successful in identifying a broken wire. Now both licence plate lights are not illuminating. (Bulbs are okay and so are both fuses). Wiper and boot lock are okay.  I suspect a further wiring fault in the tailgate. Any tips on how I should investigate if a broken wire is not obvious at the hinge between main body and tailgate? Thanks

If you can't physically see it by untaping all the wires where you can then you start at the end connector and go back to the next connector and check power or full power is getting through, for earth points and wires too, if it's not there you check the next section.

You can also look for signs of rubbing, water furring up connections, unsecured wire and connections.

VWŠkoda does seem to have very thin fragile wiring and a ridiculous amount of different fragile wunderbar fantastic-plastic wiring connectors ("Simply Clever"?).

Have a look at some of the videos here. - https://www.youtube.com/@mrautoservices7354/videos

Thank you ‘Nta16’. I’ll get on to this over the weekend, starting at the hinge. Are interior panels removable without special tools? E.g I understand from other topics the connector block ‘forward’ of the tailgate loom is behind left hand side boot panel.

You can use ordinary tools to remove the panels but if you have something plastic less chance of scratching, perhaps an old plastic kitchen spatula (or one from the kitchen drawer) can be useful, two is better thin blade and thicker blade, or just can buy plastic tools just for the job, those little orange ones.

I bought a Lidl set of 14 car trim removal tools, £7.99, different shapes and sizes but a little big for say removing the number plate light but ideal for removing the rear door interior panel (after removing the T25 screw).

That panel comes off very easily the other panels I've not tried yet but I will have to thanks to VWŠkoda very thin fragile wiring.

If you have to remove the rear door electric switch take my advice don't bother trying to do it from the exterior take the interior door panel off instead as it's easier, don't ask how I know, oh, the swearing at VW, again.

There are a few threads with photos on this forum where members have exposed the wires from body to boot door.

Let us know how you get on, if in anyway you enjoy the process I'll let you do similar on my wife's Fabia at no charge, we've (it was her choice of car) yet to get around to sorting the non-working wiring for the boot switch, just pressing the remote fob instead, !"£$%^& VW !! ARRRRR !!

Thanks again for your tips. I work in the aerospace sector - no room for sloppy design - so I share your VW frustration. ”I’ll be back” once I have made some progress ….

16 minutes ago, spig212 said:

I work in the aerospace sector - no room for sloppy design

In that case good job I didn't mention using small sharp pins to pierce through the insulator to the wires from end of cable run to what you can get at as mid-point and test this section for yay or nay, possibly adding wiggle, heat, cold, wotever might be a cause for fail/internment, then as required half the half or check the full half you've not checked and do the same to that side.

I hope I've made sense, I can get a bit too technical and jargony at times.

I don't believe in "German engineering quality" certainly not from this century but to be fair all cars are design and built with some many compromises for various reasons, and not just to pay very large wages, rewards and expenses towards the top of the companies, not that you'd see any of that anywhere in aerospace of course.

@spig212 The first place to look on any issue affecting the tailgate electrics is the nearside tailgate grommet. It just clips in and pulls out, so you'll be able to spot any fault in there in just a few seconds without taking any panels off. The cabling is far too tight on mine and gets stretched when the boot is opened and is a fairly common failing judging by other reports I've seen on the net. The offside doesn't seem as bad as there are less wires going through that.

I already have one broken wire - the blue/brown one in the attached photo that tells the body control unit that the boot is open. So my boot light doesn't work, and if I leave the tailgate open for more than around 40 seconds, the car self-locks (because it doesn't know the boot is open!) and then the alarm usually goes off as the ultrasonics pick up the air movement inside the car. Great when you're loading your shopping.......

So it's on my list of jobs to do to graft in a whole new repair section of loom. If it it this fault you have and gets repaired at a dealer, you're probably looking at a bill of £400+ as the rear loom alone is around £130. You can actually get repair sections made by Febi if you're good with automotive crimpers, but the repair section isn't exactly cheap at around £45 + it comes with the grommet and if you wanted to keep that, you'd have to get the rear window wash tube through it. I'm hoping to do the repair in situ with standard automotive cable soldered and heat shrunk at each end.

As you can see in the photo of mine, there is no point me just sorting one wire as all the rest are well on their way with the insulation being litterally stretched apart - and that doesn't happen with normal flexing faults.

What really hacked me off about this was we bought the car from a main Skoda dealer with a Skoda warranty on it, and the fault was first experienced just a few days after we collected the car. The dealer refused to accept the fault was a pre-existing one in spite of being shown the photo and tried to claim it had broken over the proceeding few days and was just normal wear and tear (on a car with less than 35K miles on it at the time). Skoda UK refused to accept it was a known issue when the wires are like guitar strings. Skoda's warranty refused to pay out because it has an exclusion on wiring. I took my case to the mediation scheme the dealer was part of (run by the local Trading Standards) and the dealer still refused to offer any evidence that the fault wasn't pre-existing, so I'd have had to take the dealer down the small-claims track. I mulled it over and decided I could fix the fault myself faster and with less stress than taking them to court, and to be honest, given how they behaved and the two other defects that they had to admit were present, I wouldn't let them anywhere near a car of mine anyway.

So even a shiny main dealer Skoda used car warranty is no protection against wiring issues, which was certainly an eye-opener.

Edited 13 August, 202513 Aug by Yorkshiremidge

Thanks for your tips too Yorkshiremidge especially with regard costs of looms. I had a similar warranty experience with a Ford Fiesta years ago where the all the dashboard lights would periodically and randomly go off in one go and randomly recover. Again, the dealer wouldn’t cover the fault cos it involved lights/bulbs. Didn’t matter that it clearly was a different fault since everything was failing. £700 later I had a safe car.

25 minutes ago, spig212 said:

Thanks for your tips too Yorkshiremidge especially with regard costs of looms. I had a similar warranty experience with a Ford Fiesta years ago where the all the dashboard lights would periodically and randomly go off in one go and randomly recover. Again, the dealer wouldn’t cover the fault cos it involved lights/bulbs. Didn’t matter that it clearly was a different fault since everything was failing. £700 later I had a safe car.

Ouch - that's some bill and sounds like it might have been a new instrument cluster? - so that is a VERY hard one for them to defend if that was the case.

Blown light bulb, a corroded connector, or wire coming loose and rubbing against something - fair enough to exclude as normal wear and tear.

But the reality is that even when you get something like a main Skoda dealer warranty, it isn't actually run/controlled by Skoda - it is run by an insurance company. If they can get out of paying a claim, they will, and to hell with the rights and wrongs of it, even if it affects Skoda's reputation. My local Skoda dealer (as distinct from the clowns we bought the car from) took photos and at least tried on my behalf to get the warranty provider to cover it, but they just refused - and the dealer admitted they had had cases before where they felt a customer claim was reasonable, only to have it knocked back. That being said, the warranty provider had to pick up the bill for one of the other defects our car had, so it wasn't all bad news.

As an aside, our other car is a TT Mk2 and they are well known for burning out the earth pin on the rear light cluster connector as its just too small to handle the current from such a big and well lit light unit. Unquestionably a design fault from new that will affect every Mk2 sooner or later, but I bet many TT owners have had that one knocked back over the years. Thankfully, it's an easy fix - you just wire in your own earth.

I forgot to put if the pin holes in the insulation required it superglue was used to fill them in, of course there are many different superglues and no doubt many more now and no telling what ones sourced from Temu and Amazon might be, and the wires and cables weren't as skinny and fragile as those that VW use. With my fat sausages I'd struggle with pins and holding two multimeter probes.

I was farting about earlier "repairing" a 5p worth £5 usb fan for my wife and although I have small hands my fingers were two fat to monoverse round and and with the plastic motor housing, flimsy metal fan and plastic covered fan guard. Getting the three tiny screws located to hold the circular black plastic motor housing to fan guard and orientated correctly required, the wire stand to be removed, three big sewing pins and my "glamorous assistant" trying not to shine the bright or reflected light into my eyes so I could line the three holes to put three pins in as locators for the three tiny screws. Tested and proved to be working at all stages after "repair" (just sprayed it with some electrical contact cleaner) confirmed at last two stages by the boss - what's the betting she plugs into her computer at her work tomorrow and the fan doesn't. To be fair it didn't have any VW markings so perhaps it might. 😁

Some good news - at least progress. Found two broken wires. See photo. Yet to find the other ends or see if there are any other broken or fraying wires.

One is black - earth or power? The other grey/red - which goes to the plate lamps.

I’m struggling to get the plastic grommet out. Flat blade screwdriver too fat. Any tips?

Opened things up. Evidence of other wires under stress - blue/red and a brown.

The black wire looks like two wires in a tiny bundle - is that the case?

I used a trim pry. You will see it has clips on the side that hold it into the bodywork.

Normally, plain brown is always EARTH.

There seems to be a bit of variation on the wiring to the heated screen element. Some are WHITE all the way from the control module to the element, some are BLACK/RED changing to WHITE in the luggage compartment, and some are BLACK/RED all the way to the element.

Some wiring diags have two earths from the heated screen so I wonder if that is a bundle of those two earths OR whether the feed and the earth for the element are bundled together. You might need to strip it back a bit to see if you can see.

@nta16. At least I’ve not needed to resort to pins to track down and home in on the fault. Re your tip about glue. Would that work to support the two wires where the insulation has broken but wires in tact still? Or is recommendation to a preventative wire repair as @Yorkshiremidge is going to do.

I recently repaired a desk fan - after stripping back the rotating mechanism needed a regrease. Works lovely but rejected by my daughter for a slight rattle.

@both. Run out of light this evening but have stripped the wire insulation back. Just need to find some suitable wire and make the repair

1 hour ago, Yorkshiremidge said:

I used a trim pry. You will see it has clips on the side that hold it into the bodywork.

Normally, plain brown is always EARTH.

There seems to be a bit of variation on the wiring to the heated screen element. Some are WHITE all the way from the control module to the element, some are BLACK/RED changing to WHITE in the luggage compartment, and some are BLACK/RED all the way to the element.

Some wiring diags have two earths from the heated screen so I wonder if that is a bundle of those two earths OR whether the feed and the earth for the element are bundled together. You might need to strip it back a bit to see if you can see.

@Yorkshiremidge @nta16 Do either of you know what the gauge of the black wire is? I’m guessing 2.5mm2 from using my wire strippers.

Showing as 2.5. Note - this is ONE of the wiring permutations I mentioned for the heated screen so yours might not be quite the same colours, and this is the one with two earths.

Edited 13 August, 202513 Aug by Yorkshiremidge

@spig212 I'm still puzzled about the documented wire colours though I have to say. The only black wire I can see in the diags is a 0.75 going into the wiper motor - and that might be the wire running alongside the broken red/grey on yours. If you look at mine, the same thinner black wire runs next to the green/white - but I also have a fairly hefty black wire too and I can't think that anything else in the tailgate would need anything that size other than the heating element.

Edited 13 August, 202513 Aug by Yorkshiremidge

The superglue was just for covering the pin holes if needed.

For wiring you can pay a bit and get a hour's worth of all the info you can download, you really need to stuff of the VIN as the wiring usually changes part year to part year and what is actually on the car when built. Do be aware all sources of information from any source are likily to have errors and omissions.

For the fan noise sometimes cleaning the fan blade well both sides can lessen noise and have the fan blade going in better balance, course it depends how much crud was on the blades to clean off.

The fan my wife brought to me was about a 2.5" wide fan blade, the metal blade was so thin she bent it when I asked her to hold whilst I firmed up the screw.

On 13/08/2025 at 23:01, Yorkshiremidge said:

@spig212 I'm still puzzled about the documented wire colours though I have to say. The only black wire I can see in the diags is a 0.75 going into the wiper motor - and that might be the wire running alongside the broken red/grey on yours. If you look at mine, the same thinner black wire runs next to the green/white - but I also have a fairly hefty black wire too and I can't think that anything else in the tailgate would need anything that size other than the heating element.

I did find in wiring diagrams a black wire going to the heater where the car variant includes a digital radio aerial integrated into the rear windscreen/heater. Can’t say by looking that is my setup.

With only a 24 hour window before my daughter disappears with the Fabia I’ve done a heath robinson solder job on the plate lamps and repaired a brown wire that was on its way to breaking. see picture - each wire fix has a heat shrink sleeve and then I’ve resorted to an outer layer of insulation tape.

For the black wire need to source a crimp - I think soldering will be a challenge with all that copper. I’ll have to wait a week before fixing this.

Edited 15 August, 202515 Aug by spig212

Having brain freeze. The heater element is protected by a dedicated 30 amp fuse. Therefore, I will need a 30 Amp or higher crimp. Can’t help thinking this will be big. Am I missing something?

I'm not convinced that super-thick black wire is an original part of this car. Might be a 'this is all I had' repair bodge previously.

Can you not take the tailgate trim off and see where it goes to?

@Breezy_Pete heading down a continuity check it goes to the demister. Got a 35Amp rated butt connector so going to repair with that.

Fair enough.

If you have any further trouble, it's probably not too hard to get to the source of these wires beyond the holes in body and tailgate, and replace the sections which go through the bellows, with splices in areas that don't flex when the tailgate is moved.