Breezy_Pete

I think so, yes. I seem to remember that access is via the scuttle area of the engine bay, and access isn't too tricky. There have definitely been a few failures documented on here so a search within this subforum for that fault code or "air quality sensor" may turn up some names of those with hands on experience of the replacement.

Rather than trying to think about it, just do the free and simple check I've suggested. A new servo is a whole heap of cost and effort compared to replacing a vac hose, so check whether the vac hose needs replacement or mending first; no matter how hard it is to figure out why it might give rise to the observations. An (extreme) example of a failing servo hose:

Tell us which engine this car has please, it's a great starting point for fault finding.

I'd be very carefully double-checking this, both by feel and phone camera images. Assuming the same questionable materials are used on your model as on mine; the hard plastic sections of the servo vacuum hose are infamous for splitting at the junctions where they are pushed over hose barbs on things like the non-return valve. If you haven't checked such junctions from all angles, have a look/feel now.

1. Not that I can see by scrolling through a few wiring diagrams. Your engine code would be valuable in getting to the correct diagram, as would knowledge of whether or not the car has start/stop. 2. No, but almost certainly wayyyy less than that. Try disconnecting the LIN connection at the alternator to see if that changes anything. 3. Fuse 20 in the cabin fuseholder appears to be for the alarm horn.

Let us know either way please.

I've added a word in square brackets above, because I'm pretty sure you meant it to be there? This sounds like a very good analysis of the failure mode. Movement in a bolted joint leads to fatigue failure. Inadequate initial tightening in the factory seems like the simplest explanation; whether by design spec, operator error or tooling (mis)calibration.

Fix the extremely common failure of the alternator load sense wiring then see how things are afterwards.

Bottom right hand corner of the relay holder in the cabin, I think, straddling two positions (Labelled V and VI according to wiring diagrams)

What year is your car Alan?

Try this: vw.current.draw.tb.pdf

Brake servo is the big black round thing at the back of the engine bay. The vacuum hose goes between there and the inlet manifold.

Looks like the choice is easy based on how many mounting holes the bearings on the car have, see here (item 26, 1T0498621, or 8J0598625): https://skoda.7zap.com/en/cz/superb/sup/2012-632/4/407-407006/

there looks to be a few variants depending on number of fixing holes and brake set-up. What year is the car, and do you know your front brake PR code?

Just spotted something in the wiring diagrams that decreases my confusion a bit. The x-relief relay doesn't appear to work quite the way I thought. In previous cars I've owned it tends to be hard-wired to the ignition switch, such that it's energised in ignition-on position, but not in the cranking starter motor position. It doesn't seem to work this way in Fabias. It is energised directly from the ignition switch in the first click round position, but then not in either of the next two positions; ignition on and cranking. But...there's another connection to the relay coil from the Onboard Power Supply Control Unit; presumably this takes over control of the relay once the ignition switch is turned further. This opens up the possibility that the relief relay can be kept energised by that control unit, independently of the ignition key position/presence; whether by programmed function or fault condition. I'll have to look into this some more

Just a thought: see if something that should not work with ignition off, actually does; e.g. the cabin fan.

AR has been superseded by BC: https://oemwolf.com/oem-parts/6q0500051ar.html#replacements

Couldn't resist de-rusting the driveshaft and getting some new paint on it, so completion of the re-booting will be somewhat delayed... Car is off the road so no rush. Thanks to all who've answered.

I made a 'pusher' to work with the biggish hammer. Went on the first hit . Just wish I'd cleaned the oak sawdust off the pusher a bit more first.

Thanks Ricardo.

I will try hitting harder after lunch. Yes, VW771 goes with that puller, and google says that's a slide hammer kit. Interestingly, the Fabia workshop manual for identical part (number) driveshaft suggests hitting, with a drift "positioned exactly at the centre of the CV joint.".

Only done one of these before, years ago on a Mk2 Golf, don't remember any trouble but this one's not budging easily. It's actually on/off a 9N3 Polo, and the boot needs replacement. Workshop manual suggests a puller arrangement, which I don't have but can make if necessary. It's just not clear which surface(s) the puller needs to work on (A or B in my picture, or both)?:

True. Double-check what happens if you disconnect the door lights, making sure interior light is off too.

@Scot5 mouse over his username, choose 'ignore user'. Problem solved.

I've reported your last post @J.R.. A mod will probably help you out shortly.