Passat 3BG Fault Code Generator for Mechanics

Good evening, everyone.


I would appreciate your advice.

Today, we were driving our Passat back from vacation. After about 250 km on the highway, the red warning light suddenly came on, and the message "Generator - Workshop" appeared. After about 20 seconds, the warning disappeared and didn't reappear for the rest of the journey (about 290 km).

Upon arriving home, I removed the belt and checked the alternator's freewheel, which all appears to be in order. The battery charging voltage at idle is 14.5V, and there are no entries in the error memory. I replaced the ribbed belt at 120,000 km during the timing belt change, and I can't see any signs of damage on it either. The alternator is a Valeo unit, and the car currently has a mileage of 156,000 km.

I'm a bit lost; how would you proceed?

Best regards, Holger.

Hello,
I've also driven the AVB and also experienced problems with the alternator. Ultimately, the internal regulator failed. Despite sometimes producing lower voltage, the alternator lasted until the car was sold at 271,000 km.
"But a fault in the MFA without any recorded error? And 14.5V at idle? That's strange. Here's something to read about it:"
/viewtopic.php?t=10825&highlight=generator
haithamina

I had the same problem with a friend's device!
However, the warning light wouldn't go away.
Despite the 14.2V voltage at idle.

The reason was a faulty solder joint in the circuit board housing.
I switched to this one, and it's been great!

Best regards, Michl.

Hi!

At the current temperatures, 14.5 V is already a bit too high. While defective alternator regulators are rare, the voltage is often too high in such cases.

As far as I know, the Lima clearances are quite tight and do not affect the Lima function.
The belt then flutters wildly.

Let's keep going, and observe.
That's why people don't just stay in bed.

Thank you, and I will observe this for now. As Steffen wrote, he won't stay down for long.


Best regards, Holger.

I would start by removing the regulator from the back and first inspecting the brushes. For this, the alternator doesn't need to be removed on a 3BG model. Disconnect the battery, remove the engine cover, and then remove the plastic cover on the alternator, and you'll be able to access it.

Here are some pictures of Valeo regulators.

Hello Steffen,


"The instructions and pictures were really helpful, thank you very much. Disassembling the regulator was easy after that. The carbon brushes still have 6mm of material left, so they are probably worn out. Given the mileage (156,000 km), should I only replace the regulator and carbon brushes, or the entire alternator? We live in a rural area and rely on the car, which is why I'm asking."


Have a nice evening.

Best regards, Holger.

Nonsense, leave the clutch mechanism alone if there's nothing else wrong. There are no noises that sound like a bearing failure, and the belt isn't wobbling, which would indicate a faulty freewheel. And even the freewheel can be replaced individually.
The carbon length of 6mm is still within the acceptable range, so that was probably not the cause of the display message. However, since the wear limit is 5mm, I would recommend replacing it in your situation. Part numbers for this component that can be found in stores are, for example:
Hella 5DR 009 728-251, Vemo V10-77-1019, or VW 038 903 803 K. I don't know where you buy your parts, but your dealer can use these numbers to find the correct item.

bartheho wrote:

After approximately 250 km on the highway, the red warning light suddenly came on, along with the message "Generator - Workshop". After about 20 seconds, the warning disappeared and did not reappear for the rest of the journey (approximately 290 km). Upon arriving home, I removed the belt and checked the alternator's freewheel, and everything appears to be in order.

Hmm,

However, the mileage and symptoms closely match my experiences with my G IV back then. It also occurred when driving at higher speeds and then would suddenly stop.

It appears that the freewheel slipped under load. Also, grease was leaking from the bearing.

How did you check the free running?
Does the idler arm wobble when the engine is idling?

Roger wrote:

Does the arm of the tensioner pulley rotate when idling?

Okay, that's the span element. I was just about to post about that too.

On the Passat, located to the left and below the generator (approximately at the 8 o'clock position when viewed from in front of the car), is a tensioning element. It consists of a roller with a small gas spring damper that presses the roller against the belt, thereby keeping it under tension.
This part doesn't last forever. You should quickly double-check it. Let the engine idle and see if this roller is spinning wildly.
Besides the roller, there's a mother sitting there. If you use a wrench there, you can move the vibration damper back and forth.
Check if it goes in smoothly and tightly, without any air pockets. Of course, do this with the engine off.

Hello everyone,

I checked the freewheel while the belt was removed. I strongly rotated the alternator pulley and then held it, and the alternator continued to spin.

I also checked the tensioner, and it seems to be fine. There's no play in it when idling, and the belt is also nice and tight.

I've already seen what a faulty freewheel looks like on my Golf (the one in my signature). The belt almost came off. By the way, the problem occurred twice yesterday, very briefly, both times after the car had warmed up properly in a parking lot. I'm going to install the new alternator regulator this weekend and will report back then...

Best regards, Holger.

Yes, and did the new regulator help?

Sorry for the late reply...


So far, it has been running absolutely reliably since the regulator was replaced.


Wishing you all a happy start to the new year!


Holger.