Octavia: 110mA Idle Current (2000 AKL)

Hello, this might not be a diesel-related issue, but I'm sure you can still help me.
A relative of mine is experiencing a quiescent current problem with the vehicle mentioned in the title. They took it to a specialized automotive electronics workshop , and the control unit for the central locking system on the driver's side was replaced. After that, the quiescent current dropped to the value mentioned in the title (it was higher before). The workshop found no further errors and gave up. Now I've been searching privately, and I've reached a point where I need a clamp meter, but it hasn't been delivered yet. Therefore, the troubleshooting is postponed.
"Anyway, power is flowing to the climate control system, and I've narrowed down the problem to approximately 15 pins. In the process, I discovered that this 'specialized workshop' apparently didn't even have a clamp meter. Instead, they simply cut the wires leading to the connector and then soldered them back together (!). I learned from the automotive trade association that soldering on the vehicle's wiring harness is generally forbidden, and if it's done, it should only be with silver solder."
That's the background information.

Now, my actual question is:
I've been thinking about whether a quiescent current of approximately 100mA might be normal. I don't believe it's normal, especially since it has a central locking system but no feedback (FFB). And even if it were, I think 100mA is too high; control units should ideally draw at least a few kOhms.
Does anyone have a target value for the quiescent current? (Not available in ESI-Tronic)

Thank you very much for your help.
P.S.: If you wish, I can also attach a photo of the severed cables.

hi.

"I don't have a specific target value readily available; I actually adjusted it based on the equipment and the number of control units involved."

In my opinion, it should definitely stop at a maximum of 60mA.

... is but a great

Quote:

automotive electronics specialist workshop

, that doesn't even have a :lol:multimeter}.
Did they also wait (for the quiescent current measurement) until all the control units had "gone to sleep"? It can sometimes take up to 2 hours.

I don't know, they were in a workshop in the Berlin area, while I'm here in the Kassel area.
So, besides the central locking system and the (leaky) sunroof (which is why the car is a breeding ground for moisture, which is probably where the problem will originate, but I don't want to have to rummage through the entire car), it doesn't really have any other issues.
"And I've been waiting like this for about half an hour, and I'll probably continue waiting like this until around 9 PM tonight. Let's see, maybe something will still work out."

oops oops oops...

I personally wouldn't just refuse to pay for the repair, but I would also charge them for the cost of a new wiring harness.

However, if there is a lot of moisture in the car, you should definitely try to remove it, especially in the area where the problem is occurring, as it could otherwise make things much more difficult.

Yes, I said that too, but unfortunately, I can't go with them.
Unfortunately, my company lacks the necessary expertise in that area to consider borrowing.
Perhaps something can be done about that over the phone...
As I mentioned, there are still about 15 pins that could be the issue, and before I take the whole car apart, I'd rather measure again to narrow down the problem.

Yep...


Maybe you should try repeating the whole process yourself.

The biggest culprits for excessive power consumption are accessories like radios (especially those with TMC), navigation systems, and phone charging stations... if they are installed. When measuring, make sure to remove any fuses.
Usually, you can find the suspects there.

It's not due to that; I figured out that the central locking system is the culprit by checking the fuses. By disconnecting the connectors, I discovered that it's the control module on the driver's side. Unfortunately, this module powers a lot of other components, which is why a fault in the comfort electronics is also a possibility.
Well, I'll look into it again in the summer. I've just roughly calculated that the battery will last for about 12 days before it's no longer possible to start the car.

(By the way, there were no error codes stored in the system's memory.)

Thank you again for the tips.

I recently had a similar problem with my Golf IV:

"The quiescent current is over 100mA. However, because the tailgate lock got wet due to a leaky tailgate wiper, there were leakage currents flowing through the microswitch for the trunk light."
However, the lamp wasn't glowing, so this was only noticed by measuring it (and by the high battery discharge when it was not in use).
After I unplugged the lamp, the idle current in my device returned to 8 mA within approximately 1 to 2 minutes (so no waiting for a whole hour).
However, I don't have a wireless charging device.

Does the noise come from your tailgate, or is it more likely from the sunroof or the interior light?

Besides the microswitch itself, the corresponding connector attached to the microswitch was also corroded. Even with the connector disconnected, there were already leakage currents.

Hmm,

If you're already soldering the wiring harness, you should also heat-shrink the connections. Using electrical tape is extremely careless. I understand that when dealing with currents in the milliampere range, you may simply reach the resolution limits of standard clamp meters. However, I would rather use a multimeter in series with the battery and remove all fuses that are not affected. Cutting any wire is absolutely clumsy.

Does anyone here, based on experience, know what the approximate maximum total currents are that can occur when connecting the battery without turning on the ignition?

Alternatively, you can measure the voltage drop across each fuse in the main electrical panel, and if the voltage drop is unusually high, convert it to current using the separately measured resistance of the fuse.

Here are a few additional tips regarding unexplained leakage currents, going beyond what has already been mentioned:

- Intermittent connections on one of the CAN buses are causing all connected control units to unexpectedly power on, resulting in increased power consumption.
- Radios with memory for traffic announcements can temporarily draw a significant amount of power.
- Retrofitted CAN adapters for radios/navigation systems can also, depending on the manufacturer, occasionally cause excessively high quiescent currents.

Okay, thank you again for all the tips. However, as I mentioned before, almost all the consumers are connected to that specific control module. I didn't want to completely disassemble the entire car and start pulling plugs everywhere. I did disconnect the interior light, though, because it's the most obvious thing to check when there's a leak in the sunroof, but it wasn't the cause (at most, it could be the wiring leading to it).

So, a clamp meter with a resolution of 10mA should definitely be available in a specialized automotive electronics workshop. I now have one privately that can be used as an adapter for a regular multimeter (up to 60A with 10mA accuracy), which I bought from ELV for €70. This is not meant to be advertising, but just a tip (I think it's very inexpensive): clamp meter.

Again: With the "pull the fuse" option, I have already found the relevant fuse, but the F38 is for the green-yellow . I narrowed down the problem by unplugging the green connector from the central locking control unit on the driver's side, which caused the current to stop flowing again. As I mentioned above.

Unfortunately, the car, where I have my pliers, is now about 500 km away from me. However, I will be able to look at it again in about 3 months, and I will post here again with what I find out.

Regarding the maximum currents, I cannot provide a specific value either, but I would also be very interested to know.
It definitely malfunctions quite severely, for example, in the current A6 model.

BeKli wrote:

So, a clamp meter with a 10mA resolution should be available at a specialized automotive electronics workshop . I now have one privately that can be used as an adapter for a regular multimeter (up to 60A with 10mA accuracy) that I bought from ELV for €70. This is not meant to be advertising, but just a tip (I think it's very inexpensive): Clamp meter

.

I don't want to take away your faith in technology, but clamp-on measurement is fundamentally very inaccurate. Much less accurate than what is suggested here with the stated resolution. That's why the ELV description also uses the term "basic accuracy." The measurement accuracy is always related to the measurement range end value. You should expect +/- 1.5% here. This means that with a maximum assumed current of 20 A (= 200 mV) in the small measurement range, you have +/- 300 mA. In the large measurement range, you have +/- 1.5% of 60 A = +/- 900 mA. In addition, there is the measurement accuracy of the multimeter used for the display, for the converted voltage value... You can clearly see that the advertised 10 mA resolution does not correspond to 10 mA accuracy. This is just clever marketing.

We use professional DC clamp meters from Hioki in our company. When trying to measure currents in the mA range with these, you get surprisingly high deviations compared to a series measurement. The measurement principle itself is the Achilles' heel here. There are simply too many inaccuracies involved, starting with the exact right angle of the conductor in the loop and not ending with the wandering zero point or the influence of external fields.

IMHO, the measurement accuracy is simply not sufficient for truly detailed quiescent current measurements in the automotive sector. Such measurements can only be done in series or - somewhat accurately - by measuring the voltage drop across the fuse. That's also why I asked about the currents involved. In the 20A measurement range of the multimeter, the accuracy, according to the calculation above, is completely useless, and below that, mine only has a 200 mA range, whose fuse will hardly survive the inrush peak when connecting it to the battery .

VW, on the other hand, sees the voltage measurement across the fuses as part of the troubleshooting process for identifying the root cause of errors .

The troubleshooting tips in the other post were mainly intended for other readers who might also be experiencing a standby power issue.

Quote:

Does anyone have a target value for the quiescent current?

"100 mA is definitely too much for the Octavia. Without a hands-free phone system, I would consider 20-30 mA to be the maximum acceptable value."

Roger wrote:

...among these, my measuring device only has a 200 mA range, and its fuse will likely not withstand the inrush current when connected to the battery .

Therefore, when inserting the fuse (or connecting the battery), bridge the meter. Once the fuse is in place (or the battery is connected), simply remove the bridge.

Regards,
Guste.

@guste:

Good tip, that way I might be able to measure it directly at the battery.

Regarding the accuracy issue: I also measure the quiescent current in series with the battery. The value displayed by the clamp multimeter is actually irrelevant; I only need it to see which wire the current is flowing through, and with a resolution of 10mA, it should be able to do that (which is why I think it's well-suited for troubleshooting quiescent current issues). Measuring the voltage drop across the fuse is not helpful because the fault is already localized, and the fuse has already been identified.

It might be worth checking with the diagnostic tester to see if all the doors are reporting as 'closed.'
Or perhaps some other switch is not responding correctly.

Once you find the cable, it's likely a connection to the TSG, and then what? Or do you think there's a leakage current within the wiring rather than a component failure?

If you already know that the TSG is causing the electricity consumption, then I would investigate why it's doing that. There must be a reason.

If a component was swapped, was the corresponding control unit properly coded?

The 'Komfort STG' (Comfort Control Module) in some A4 models should not be coded to the 'SZV' (Start-Stop System) because doing so can lead to increased idle current and battery drain.