rum4mo

It could just be the temperature flap motor that is faulty, I've had that on a VW Group car, demanding Hi and then a couple of minutes later demanding Lo and repeat this quite a lot of times, that can sometimes clean up the potentiometer contact or track and get it back to working okay for a few hours/days/weeks. If that does help, I'm very surprised that your Skoda dealership did not read the A/C controller memory for faults before doing any changing of parts - or maybe this has just failed?

I'd need to connect up to my wife's 2015 Polo to see/remind myself how you "get into things" - or, have you looked on the Rosstech website, it normally gives guidance for some standard procedures, it will probably show you 2 methods depending on age of car, your car will be the newer version. Edit:-, ah, right, I thought that you had VCDS or similar, you will not find anything by just looking in via the infotainment system of your car.

@Eccles, when you go into the area where the battery info is kept, ie look into CAN-GATEWAY, and you should find the BMS sub section and in there you should find all the batteries info like, capacity (Amp hours) + technology + manufacturer + serial number - all you need to do here is to change the last digit, or to help you remember when you fitted it, delete the last 6 digits and replace by the date. If you like keeping an eye on things, look into Advanced Measuring Values and note what you find before making the serial number changes, then maybe again in a few weeks to see if things have changed and if so make your battery look a lot healthier - there should be a long list of stuff in there so you will need to scan down until you come across the ones relating to the battery. The last time I did this sort of thing was back in mid February so facts are a bit vague, sorry. Edit:- my my wife's 2015 VW Polo and my mate's 2018 VW T-Roc have the stored value for the battery serial number as 1111111 - ie lazy sods in the factory are not inputting the serial number from the actual battery being fitted, my daughter's 2019 SEAT Leon Cupra has all the correct info for the battery fitted into her car at the factory, so it can be done and some VW Group factories do make the effort, maybe Skoda do.

The car does not know its got another battery in it, why if you have a means of communicating with the car, did you not change the serial number when you changed the battery, I'd always do that or more if changing the capacity or technology of the battery?

AC hissing does sound a lot like it is short of gas, so needs recharging, it seems like some modern systems like a recharge at 4 year intervals, VW Group would prefer you included a recharge every 2 years as it makes them more money.

@Eccles, did you do any recoding so that the car knows that the battery has been replaced? If you old battery turned out to have become a "sick", and that is why you have replaced it with exactly the same type/technology without recoding it slightly, then the "smart" area of the battery charge maintenance will just be thinking that nothing has changed, though it will readapt the charging profile to suit that new battery eventually, or was the car recoded after the new battery was fitted but the new battery was well down in charge when you fitted it?

One thing that I'm not sure that you have confirmed, with the AC switched off, does the cabin fan run at a steady speed if you demand lowish temperatures? What I'm trying to get you to do is to make sure, to start with, if this is a cabin fan or its control issue, after proving that the cabin fan works okay, then move onto what has been suggested above. No magic, just needs you to work through all the basic stuff first before moving onto the chiller side of things.

@Bertie90, that was the Low side you were connecting that pressure gauge into, as others have said, it sounds like the condenser fan or its control is not behaving. You always fill from the Low side.

Or maybe even ATS, look for their £38.99 offer, I used them last month, make sure anyone that works on your AC refits the charging port dust cover - I didn't so had to buy a new one which cost a bit!

Ouch, like you, I'd be expecting it last a lot longer than 5 years, our previous 2 VWs normal "switch blade" fobs lasted over 13 years, and the 2000 Passat ones are still working okay! Current 2011 S4, stuff in the dash fobs both good, current 2015 Polo "switch blade" normal fobs okay.

Time will tell, it could just be an electronics failure in the alternator's regulator/control pack, they tend to "go" without any warning. For example I started my daughter's late 2009 Ibiza up, reversed back up the driveway and as I stopped at a give way 300 meters later the charge (failure) warning came on, I turned round and took another car. Checking that car out proved the alternator was not charging so with like little chose of buying parts locally, I bought an exchange Bosch same rating one at a good price from ECP, and that sorted that out. The plan was for that daughter to keep that car for a while, so I just wanted it sorted out as best I could, that alternator when removed looked as good as new - but it was faulty, the ECP guy had never seen a "good looking" clean Bosch alternator fail before, always a first time.

I bought a Draper Impact grade deep 36mm bihex socket and that worked okay - but that was bought back in maybe 2007.

I get the impression that that family of gearboxes fitted to 1.2TSI 16V Fabia/Polo/Ibiza/A? both the 5 speed and 6 speed, seem to be a bit "cut price" and maybe also the clutch assembly, going by some of the comments/posts flying around. The 6 speed in my wife's 1.2TSI 16V 110PS 2015 Polo was okay until I handed it in for the second time complaining about the drive drive clunking/shunting noises due to the upper gearbox mounting being apparently failed or inadequate, first time they did as VW advised, which was to remove that bonded mounting slap what looked like copperease all over it and refitted it, when that fix only lasted a few weeks, they removed that failed or inadequate mounting and replaced it with the TDI equivalent, that sorted all my previous issues out and still has, but when driving the car away from my dealer, after that warranty fix, the gearbox whine in 1st and 2nd was very obvious as with time has become other gearbox noises. I fully expect to need to either get that gearbox sorted while we own that car, or find a better box from somewhere else - source as yet unknown! I'll watch your progress with interest, do Getrac or anyone else supply a sensible gearbox for these cars at a sensible price, no straight cut stuff, just higher durability and maybe higher power/torque rating?

Not a Fabia but a VW Group small car of the age group that MK2 Fabia is in:- my daughter was complaining about a noise like a heat shield coming loose under her late 2009 Ibiza 1.4 16V 85PS SC, so I got her to bring it to me, kind of expecting the front flexi to have failed so checked up on the availability of a front exhaust repair section to save paying to replace the cat as well - although being quite happy to need to fit some bits of tin under some heat shield retainers. In the event, the front flexi looked okay as did the heat shields, but what had failed were BOTH clamps on the exhaust joining sleeve under the centre of the car! Now one failing at that age is okay, I had that on my old Passat 4Motion when it was that age and I just replaced all 4 clamps - they just rot with salt and water. As I had initially bought the wrong size of joining sleeves for that 2000 Passat years ago, they were still available to use and the clamps were the correct size - nice when something only takes 30 minutes to fix! I'm just bringing this up as it might be the right time for some people to check the condition of these clamps - before they fail and cause other problems/inconvenience, just have a look under the car below the line of the front seats.