trickyskoda

Thanks both for your help 👍🏻👍🏻

Update: Wigan alternators tested the alternator this morning and conceded a diode must be leaking. The unit was replaced and I've just put the alternator back on the car and so far so good! the alternator is not causing any unwanted current drain. So it would appear that I was unlucky enough to have two faulty replacement units. Out of interest, there is a 5A fuse for the "Phone" circuit in the engine bay fuse box. This now seems to be drawing 200mA when the car is asleep... it may turn off after a while but what is the actually powering ? Since there is not a phone in the car. Thanks again,

The alternator is off the car again. Taking it back to be tested tomorrow so let’s see how that goes! Will update.

@Graham Butcher interesting that you’ve worked in refurbishment. In your experience would they change the diodes ? Or just refurbish the mechanical parts, bearings etc. I assume they would just spin it up and check an output voltage is present.

Yes, it’s bumper off and front end pulled out an inch or so to make room for it. Not the end of the world but not a fun job!

Thanks very much @Breezy_Pete . It is a direct connection then. Looks like I’ll be putting a third!!! Alternator on it then, I’ll speak with wigan alternators tomorrow and get their take on it. Third time lucky perhaps? I wouldn’t mind as much but it’s a pig of a job on the superb to change.

Thanks Graham, I wonder if I could be so unlucky to have not one but two faulty replacement units, and it is the alternator after all ? Further info: This morning I have monitored the quiescent current whilst unplugging the two pin plug off the back of the alternator. This did not make any difference. I'll discuss with Wigan alternators on Monday (where I sourced this part) but in the meantime, it would be good to know if that wire is spliced anywhere else as there could be something else at play if so, Thanks again,

@Breezy_Pete that would be great if you could, KN60JVD. If you need the VIN let me know. @Graham Butcher as mentioned this one is new (fitted a few months back). Is the diode pack/ regulator all part of the alternator unit ? If one of the diodes was leaking, why would the issue clear if the wire is disconnected then reconnected ? Thanks again for you help

I've taken a video to show exactly what's going on: Am I right in thinking that wire is straight to the back of the alternator ? Or is it spliced anywhere else ? This alternator has a two pin plug, not sure what they are doing either. Thanks again,

@Breezy_Pete - That was the original alternator and failed at around 120K (car is now on 138K). The current unit is from Wigan Alternators, I can't remember the brand now but the part number was sourced from the VIN so I assume is correct. @Graham Butcher No, the system was not re coded. I was fully aware of this but decided the worse case is the battery is being over charged and therefore has a shorter life. I didn't think it would solve the issue I'm seeing. However, I have always charged/ jumped the car directly from the battery terminals, I was not aware that this is bad practice. For what it's worth, I don't think I've ever charged/ jumped the car prior to this issue, but it's been jumped plenty of times since :) As Pete has just posted (as i'm typing), I don't think mine has a BMM, since it's pre stop start. I'm not certain on that though.

Morning Pete, I've measured across the strip fuses this morning, all 0mV apart from SA1 (Alternator). Sure enough, I then removed the alternator wire and the current dropped to ~30mA. I then re connected the wire and it remained at ~30mA. Some more info on the alternator as follows (as mentioned, I changed this recently). Winter 2023 the alternator completely died and I just about managed to limp the car home. On the run up to this point (for a few months), the battery light remained on after starting the engine. The light would turn off again after I started driving. I swapped the alternator for a new NAPA part. However, this was never right. The alternator worked, but only started charging when the car was revved over ~1500RPM, at which point the battery light would turn off and when measuring across the battery terminals, the voltage would jump to a healthy 14.3V ish. I ran the car like this for a year, giving the car a small rev on start up with no problems and in the meantime tried to find the issue. In the end, winter 2024 I changed the alternator AGAIN for an OEM refurbished part and the alternator now behaves as it should. i.e. I start the car and the battery light turns off straight away. I also managed to get a refund on the NAPA part which was nice. At this time I also put a new battery on the car just in case this was causing any issues. Hopefully this gives some clues as to what might be going on, I wonder if the NAPA part was never actually faulty? Despite the OEM refurb working as it should. Thanks again for your help,

Hi Pete, I retract what I said! I have not measured across the strip fuses. In fact, I didn't realise they were strip fuses. I will do that fist thing tomorrow and see what I get. I assume SA5 is the feed to the internal fuse box ? I also read on another thread that someone had an issue with an electric seat, but this was a circuit breaker type setup as opposed to a fuse, not something I've heard of before but wondering if there is any mileage in that.

Hi All, I'm hoping for some help with an annoying issue on my MK2 Superb, whereby the battery keeps going flat! Most recently to the point where the car would not unlock (totally dead) after 5 days away. The details are as follows: New battery, new alternator, both fitted by me. Quiescent current when the car is locked in "deep sleep" is around 350mA (hence the battery going flat so quickly!) I would expect to see <50mA in deep sleep. Interestingly, If I disconnect the battery completely, then reconnect, unlock the car and lock it again, the quiescent current will drop to around 30mA which is about what I would expect. It's only after I start the car that the issue resumes. It's as if the act of starting the engine engages something or activates a module that never goes to sleep again ? As far as trying to diagnose the issue, I've measured the voltage across every fuse in the engine bay and cabin compartment. In both cases, tricking the car into thinking the bonnet/ doors are shut. I've taken this even further and removed each fuse one by one, and the none of them make any difference to the 350mA quiescent current. The only red flag is a cheap Chinese radio (A-SURE) that was in the car when I purchased it. However, I've both removed the fuse and removed the radio completely, the issue still persists. At this point I'm totally out of ideas, I'm loathe to think it's a chafed wire since if I disconnect the battery completely, reconnect and do not start the engine, the issue goes away. For what it's worth, I am an electronic engineer by trade, so use multi meters/ oscilloscopes etc on a daily basis and fortunately have access to good quality kit. So i'm pretty certain my measurements/ method are sound. Are there any common issues regarding parasitic current on these cars ? And where could the current be going that not a fused circuit ? Thanks very much in advance for your help, 🙂