Hello everyone, 

 

I have recently bought a Skoda Octavia 2 FL VRS 2013 2.0 TDI CR 170HP in great shape. However, I have experienced a small issue with it during some of my latest drives. The previous owner has already told me about it and how he tried to fix it but it seems like the issue came back now.

 

The problem is that with no consumers at all, the voltage shows about 13.6V both on the 12V interior socket and on a multimeter reading taken from the battery when the car is running. As far as I knew about this, the voltage should be around 14,5V when the car is running. When I turn on all the consumers, like main beam, high beam, fog lamps, climatronic to max, the voltage drops incredibly hard to almost 12.9V while the engine is running. 😔 I have noticed this issue because sometimes the rpm would go to 1000 rpm when not moving, and I guess it was some kind of protection so that the voltage would not drop even lower. I don't think it was the DPF regeneration which caused the 1000rpm increase, because it was happening far often that it should be.

 

The previous owner told me that the alternator has been rebuild from scratch since he thought that was the culprit. The battery is almost brand new and he also did a test to it and there were no issues there either (there's none now also, with the engine off, the multimeter shows 12.9V on battery). He also told me that a wire, which came from the alternator (i guess) to the engine compartment fuse box (the one on the right side of the engine), was observed during an inspection to be worn out so he fixed it. Then he hold me that the issue was gone for that moment. 

 

I don't know how to check for more information but this is all I got for now. Maybe you can help me diagnose the issue even more. 

 

Thank you for your time and patience!

 

 

 

 

Oh and I forgot to mention that I did a full VCDS diagnosis and there were absolutely no error pooping out from it. Everything was clean.

Guess you are going to do some systematic testing of the charging system, alt output, voltage, voltage drops on main conductors to alternator vs battery etc. Or take it to an auto electrician. 13.6V is not far out of spec is it?  Is the charge / alt light showing on the dash, when the engine is not running,  what about when running and you turn on the consumers?

49 minutes ago, WCKD said:

  I have noticed this issue because sometimes the rpm would go to 1000 rpm when not moving, and I guess it was some kind of protection so that the voltage would not drop even lower. I don't think it was the DPF regeneration which caused the 1000rpm increase, because it was happening far often that it should be.

 

 

Is that an increase of 1000 rpm, or an increase to 1000 rpm?

 

I'd guess the car has not got stop-start, or that it is turned off (or you would have mentioned whether that was still working correctly).

52 minutes ago, WCKD said:

The previous owner told me that the alternator has been rebuild from scratch since he thought that was the culprit. The battery is almost brand new and he also did a test to it and there were no issues there either (there's none now also, with the engine off, the multimeter shows 12.9V on battery). He also told me that a wire, which came from the alternator (i guess) to the engine compartment fuse box (the one on the right side of the engine), was observed during an inspection to be worn out so he fixed it. Then he hold me that the issue was gone for that moment. 

 

 

I can only guess that this wire was part of the smart charging system. and may have shorted to ground, damaging whatever drives it. If that was the pwm output that adjusts the alternator output for different conditions, you might get this sort of symptom. Have to emphasise '...might...' and '...guess...'.

19 minutes ago, TheClient said:

Guess you are going to do some systematic testing of the charging system, alt output, voltage, voltage drops on main conductors to alternator vs battery etc. Or take it to an auto electrician. 13.6V is not far out of spec is it?  Is the charge / alt light showing on the dash, when the engine is not running,  what about when running and you turn on the consumers?

 

Thank you for your reply. The battery light is showing along with the dashboard staging feature when I turn the key to Accesories position. After the engine is turned on, it disappears and never comes back on.

17 minutes ago, Axle_of_weasels said:

 

Is that an increase of 1000 rpm, or an increase to 1000 rpm?

 

I'd guess the car has not got stop-start, or that it is turned off (or you would have mentioned whether that was still working correctly).

 

I can only guess that this wire was part of the smart charging system. and may have shorted to ground, damaging whatever drives it. If that was the pwm output that adjusts the alternator output for different conditions, you might get this sort of symptom. Have to emphasise '...might...' and '...guess...'.

The increase is to 1000-1050 RPM. The car isn't equipped with stop-start feature.  Thank you for your reply.

What is the voltage when you increase to 2000rpm and all major consumers on? I'd be happy with 13 to 14v. Ideally 13.5 or more but at lower end it should still be charging.

 

Has this caused any starting or electrical issues? 

1 hour ago, TheClient said:

What is the voltage when you increase to 2000rpm and all major consumers on? I'd be happy with 13 to 14v. Ideally 13.5 or more but at lower end it should still be charging.

 

Has this caused any starting or electrical issues? 

When I increase to 2000rpm with all the major consumers on, the voltage drops to 13V (sometimes even 12.9V). Actually it doesn't make a difference if I press the accelerator pedal to 2000rpm or just leave it at idle at ~750rpm, it will still show around 13V with all the consumers on. What intrigues me the most is that there is also another anomaly and I don't know if it's related to the voltage or not, but at idle, the rpms fluctuate a lot. I have attached 2 videos here showing the issue I'm talking about. One is a graph with the fluctuation at idle (which seems big to me) and the fluctuation at ~1100 rpm when I have my foot constantly on the acclerator pedal (which has a lot less fluctuations). The other video is showing the fluctuation of the voltage and rpms in the same time, again pretty strange. 

I do not believe the possible low voltage situation is affecting the idle. The ECM has no feedback loop to increase idle to compensate for a low charging current or battery depletion AFAIK. 

 

I can see the idle is creeping up. 

 

Search for Golf GTI mk6 surging or hunting idle, fast idle etc. Will bring up the usual suspects for that sort of issue. Vacuum leak of PCV oil separator faillure probable first places to start.  Same EA888 engine in GTI mk6 as in Oct 2 FL Tsi. 

 

Unless you can do some fault finding to isolate where the problem is, I would take to an Auto Electrician, ask what they would check first. Maybe put the alternator on a test rig first and measure output out of car environment. Otherwise, wiring fault finding....... If there is a fault. At present it is not causing any electrical gremlins or faults or difficulty starting? So maybe just leave it until it causes an issue if you want to avoid costs.

 

Of course, based on the laws of probabilities,  these sorts of faults always rear their heads when you least want them to, like being 100s of miles from home, in the rain ... late at night.... make your choices!!

 

 

8 minutes ago, TheClient said:

I do not believe the possible low voltage situation is affecting the idle. The ECM has no feedback loop to increase idle to compensate for a low charging current or battery depletion AFAIK. 

 

I can see the idle is creeping up. 

 

Search for Golf GTI mk6 surging or hunting idle, fast idle etc. Will bring up the usual suspects for that sort of issue. Vacuum leak of PCV oil separator faillure probable first places to start.  Same EA888 engine in GTI mk6 as in Oct 2 FL Tsi. 

 

Unless you can do some fault finding to isolate where the problem is, I would take to an Auto Electrician, ask what they would check first. Maybe put the alternator on a test rig first and measure output out of car environment. Otherwise, wiring fault finding....... If there is a fault. At present it is not causing any electrical gremlins or faults or difficulty starting? So maybe just leave it until it causes an issue if you want to avoid costs.

 

Of course, based on the laws of probabilities,  these sorts of faults always rear their heads when you least want them to, like being 100s of miles from home, in the rain ... late at night.... make your choices!!

 

 

Mine's 2.0 TDI CEGA, not EA888 TSI from the GTI. The issue isn't causing anything to the normal behaviour of the car right now, but I knew from my previous cars that it wasn't normal for the voltage to drop that much. The car starts as it should be. Thank you for your replies, I really appreciate!

Argh right. OK, sorry I assumed FL TSI but your already posted in your opening post the type.  Well give google a go with searching for fast idle on VRS TDI  or VW CEGA or similar.

 

Take a voltage reading after letting the car stand overnight. Preferably without having to unlock and wake the car. Then compare that to the voltage at idle with all the consumers on, if it is higher the net position is still charging!