Breezy_Pete

There are more than this, and most of those will only be powered under certain conditions. The only one that you should always see 12V at is pin 92. This feed should also be found at the connection '85' for relay no. 1 in the e-box. All the other feeds are dependent on ignition switch position and other factors. The feed from cabin fuse 1 to pin 87 of engine ECU should only be powered when ignition is on. The connection between ECU pin 69 and terminal '86' of the relay no. 1 must be pulled to ground/0V by the ECU to energise the main relay (no.1) which then feeds power to pins 3, 5 and 6 via fuse 13, which I expect are the ones you have probed?

Double check cabin fusebox fuse 1 (10A), and under-bonnet fuses 10 (5A) and 13 (30A). Which pin/pins at the ECU connector did you find lack of power at?

I'm confident enough to say that test isn't worth doing, actually. The car can't tell the difference between an unconnected trailer light board and a blown indicator bulb unless you tell it there may be a trailer connected via that coding change.

I don't think it would do that double speed thing, but try it by taking out one bulb from trailer board.

Engine ECU pin number 21 in the info I'm looking at, not sure why the disagreement with your diagram.

PM me if you'd like to consider a repair by post. I'd replace the original wiring in the 'flex zone' with extra-flexible ones of appropriate gauge, solder joined and sleeved beyond, in the door area. In terms of part number, there are usually enough variants to make scrutiny of the part number label on your existing loom preferable.

It's the other (white/green) wire you need to check, the one to the engine ECU from pin 1 of the brake switch connector, I think. If you can confirm your engine code I can tell you which engine ECU pin it goes to.

It's a requirement in theory, either an auditory or visual confirmation, so you can tell if one's failed. In practice, I don't think they test towing electrics of the 7-pin variety at MOT IIRC. Won't work if it's an LED lightboard btw, unless you add some resistors in parallel to make them look to the control unit like proper bulbs.

Perfect. If you look in the owners manual you'll see there's a second warning light that should work when you have a tow connected, giving a visual confirmation that the trailer indicators are working (when they are). Should be a dead easy VCDS recode of the onboard supply control unit to enable it. You just add 1 to the existing coding.

Which ECU pin number did you follow to the brake switch connector? Wire colour?

How did the towbar get wired in? Have you got the towing indicator light confirmation on the dash going?

Factory fit battery part numbers, and descriptions, for 2015 mk3s here: LLLParts

The ignition switched (Kl15) supply to the pump module is from a 5 amp fuse (cabin fuse 16) so I think that would blow if there was a short inside. The Kl30 fuse is the strip fuse in the battery fuseholder, but a problem with that wouldn't interfere with any other systems, like the engine as far as I can see. See if you can increase the frequency of failure by adding a Kl15 load, say by switching on the rear wiper. Edit, no, that won't do, it seems to be fed from the 75x rail, not Kl15. Does the car have heated seats? That looks to be fed from Kl15.

Please let us know when you find/solve the problem.

I'd whack another on there if it were me just to rule it in/out, only a few quid. Whereabouts are you?

Not sure it'll be relevant, but as far as I can see these are the various power feeds to the circuitboard that aren't just straight in and out of a relay dedicated to that item, e.g. wipers: a permanent 12V power feed from cabin fuse 22 via the red-yellow wire at XP2/1, a 'key in ignition' (T86s) switched feed from fuse 19, into XS4/2, an ignition on (T75) feed into XS4/11, an ignition on (T15) straight from ignition switch to XS4/12 and another permanent 12V feed from engine bay fuse 11 into XS4/5. It almost looks like a more global electrical problem to me, like an ignition switch 'iffyness'.

This caught my eye today, the 1's making the spacing look unusual:

Maybe this set-up doesn't require any such adaptation? Are they not pressure sensors, rather than pressure switches? i.e. they actually output numbers

Cos it's generally only a small fraction of the full list, maybe a fifth, or even a tenth Ken.

So? Who's forcing you to click and read?

Stop clicking on the thread, duh.

I just tried Nige's link out of curiosity, and at a glance the only difference to what a Skoda dealer emailed me is that this has a production date where the dealer version only had a delivery date. Quite a significant difference in this case, made on 16/11/04, delivered 01/03/05. PDF link was sent within half an hour of purchase.

Where does the wiring diagram you are looking at show as the origin of the 58b power rail? I guess the light switch? If so see if it is is present there when the switch is on, then keep following it to wherever it goes next. The number-plate lights on the rear of the car may be powered from the same fuse, so see if they work or not.

You may or may not know, but that site isn't UK based despite the Web address. Will likely be shipped from Berlin, which seems wasteful and problematic if a return were required.

No, the adjuster for the backlighting brightness, near the exterior lighting switch.