Breezy_Pete

That'll be it.

My understanding is that if the shear coupling has broken you'll see most of the pulley rotating whenever engine is running, but the bit in the middle won't be. The bit inside the pink circle here: Awkward to see but careful application of phone camera on video may help. This shot is from below, with undertray off.

Yep, as long as the radiator thermoswitch is OK, but on A/C cars it's very lightly loaded as it only carries the relay coil currents for the control module, rather than the much higher currents that the fan uses.

Aircon will still start working* even if the fan doesn't work at low speed, but the refrigerant pressure will rise higher before the high speed action is triggered, and this will cycle on and off very noticeably. If the low speed is working, that'll just quietly run more or less continuously with A/C on in warm/hot weather, keeping the pressures roughly steady and everything optimised. It's more a theory than anything, but I suspect if the pressures are regularly higher due to low speed function failure, there will tend to be more leakage at o-ring seals, and so more frequent regassing needed. * if there are no other things stopping it like low refrigerant, mechanical failure etc. You really need to know what the fault codes mean.

I doubt it would be anything else, unless the car doesn't have aircon, in which case I'd suspect the radiator thermoswitch. What price is a new fan module? I would say that they're usually pretty reliable, so consider 2nd hand unless new is very reasonable. If it starts up again when you reconnect the battery, you could try undoing the wire end of strip fuse 3 above the battery and lifting the crimp/wire clear away to stop it. May well be worth checking the low speed function, easy if the car has A/C, just switch that on, set it to cool and wait a short time. (Different fuse does the low speed, blade fuse no.8 over to the right of the strip fuses, under a removable cover.)

Did you observe the fan running at low speed as well as full speed? I feel sure that the test will include both; low, followed by high. High/full speed is very obvious/loud, the other is subtler and could easily be missed unless looking at the fan. Low speed failure is very common, full speed much less so. On your car low speed just uses 60W of 'lectric, full speed 250W. Low speed failure means that either coolant temperature or refrigerant pressure have to be significantly higher before the fan spins up.

There's something I don't know. Where is Thant anyway?, don't know that either. I know you can test the fans using VCDS which will be talking to the HVAC module (Climatronic control unit), so it probably is possible via the Climatronic self-diagnosis stuff.

Blade fuse #9, 5 Amp? That's a feed to one of the relay coils inside the fan control module, I seem to remember. Yeah, access can be a right pain on the thermoswitch, and be careful not to damage the connector latch as you unplug it. If you don't know the knack for VW-group type ones, youtube has various tutorials. I think any leak form the condenser would tend to be all-or-nothing, so you would have lost the lot. Except if it were at the connections where there's an o-ring that can leak gradually, probably only when at high pressure. That's one good reason for making sure the fan(s) work fully, as the system pressures will be better regulated if the fans are doing everything they should.

If the car is properly 'asleep' the quiescent current should be around 0.02A (20mA) or less. To get the car to go fully to sleep whilst still having access to measure the current is the slightly tricky bit. My preference is to open the bonnet, then flick the bonnet latch fully shut with a screwdriver (so that if there is a microswitch sensing the openness of the bonnet it will see it as shut, only cars with alarms fitted have this, I think). Then loosen but don't remove the battery negative clamp, so that you can easily pull it upwards away from the battery with fingers. Leave it connected/touching. Close all doors and lock the car. Wait at least 30 minutes. There is a relay inside the onboard supply control unit whose coil is powered for this long by default. Put your multimeter onto mA dc setting, with probes plugged into the appropriate holes. Place one probe vertically downwards through the battery negative clamp onto the centre of the battery post. Ask an assistant to hold it there for you, that makes the next bit much easier. Now put the other probe onto the battery negative clamp and hold it there without losing contact as you slowly lift the clamp up away from the battery post, without touching the other meter probe which it will now be surrounding. As long as the clamp doesn't touch the other meter probe, you will now have a true 'asleep' quiescent current reading on the meter without having woken the car by interrupting the power supply. Don't forget to pull the bonnet release lever in the cabin before trying to shut the bonnet afterwards, or it will hit the closed latch with a bang.

Don't go mad with rapid closely-spaced repetitions of starter motor on/off action. Each time the starter solenoid is switched off it sends a reverse-voltage spike through that diode, generating a little heat. Do it too often without enough time for it to lose the heat and you may fry it again. That might be what happened when your autospark was on the case.

Cheers. So just merging the solenoid valve into the vacuum motor, by the looks of it?

Can you tell me which mk2 engine code(s) use(s) such a thing so I can learn about the 'obvious' difference, please?

N75 Charge pressure control solenoid valve is one of the three solenoid valves inside the 'vacuum block'. Fuse 24 supplies all three.

Yep should be the same then. Don't actually need ignition on to test the low speed (when you link brown to brown/blue), but you will for the high speed.

Check cabin fuse 24.

What year is your car? Just so I can double check that that is all correct for yours.

Probably, but you'd have to remind me/link me to what I said.

No clutch on these, so everything you can see at the pulley end of the compressor should be turning as one.

Sounds like their initial 'it's user error' must have been a blatant and knowing lie, if they had eyeballed things from the inside at that point. If they do not offer to replace clutch and gearbox (assuming the independent assessment is that that is damaged more than cosmetically?) under warranty, seek legal advice promptly; and yes, they should definitely be supplying a courtesy car.

Recommended retail price for the washer quoted by the OP is indeed over £3, VW, Audi, Seat, Skoda N0138157 WASHER (allcarpartsfast.co.uk) See just under the £2.82

I bought the 3 o- rings required and did them myself. A few quid. I paid to have the remnants of refrigerant taken out (illegal to deliberately vent it to atmosphere), then swapped the o-rings, then took it back for refilling.

If you're doing the other side too, the colour contrast should be more obvious, the negative there is brown/blue, positive blue.

Right one in your photo.

One has a brown stripe. At a guess, that's the negative.

If the system has ever had dye added you can see leak sites pretty clearly in low light conditions with a cheap UV torch (£10?) The hose connections' o-rings on the high pressure half of the circuit are where I saw leakage from on our 2005 car. Worst one was the compressor outlet fitting I think, followed by the one going into the expansion valve at the bulkhead. Can't find the photos just now but the leakage showed up bright green under UV light.