Flickering Interior Lights: Causes & Solutions

Hello everyone,

Now I've read several posts in various forums, but I still haven't found a solution to my problem.

"For about a year, my Golf 4 TDI has been experiencing an uneven engine idle and rough running when electrical loads are turned on (e.g., Climatronic, rear window heater, etc.). When I also turn on the interior lights, I notice that they flicker. Above idle speed, the engine runs smoothly again, and the flickering of the interior lights disappears. When I turn off the electrical loads (Climatronic, rear window heater off), the flickering stops."

Initially, I suspected a low idle speed and increased it to 945 RPM using VAGCom. However, I then realized that my TDI has an idle speed control system – when a load is applied, it automatically corrects to the set value of 945 RPM. This did not solve the problem.

Okay, so I measured the on-board voltage with the engine running. It's approximately 14V at idle with no electrical load. When I turn on the climate control at its lowest setting and the rear window heater, I see the on-board voltage fluctuating between 13.7V and 13.8V, while the interior lights flicker simultaneously, and the engine starts running roughly again (at idle speed).

"The alternator seems to be working correctly, right? Unfortunately, I have a Hitachi alternator installed, which has an integrated regulator, so I'm ruling out a regulator replacement. Also, I don't want to spend around 200€ on a new alternator right now, and I'm running out of time because I'm going on vacation in about two weeks."

"Now's the time for expensive advice - does anyone know this problem? Should I perhaps check the wiring of the alternator, or the ground connections under the battery holder (I've only read about it, but I have no idea where they are located)."

The error memory is empty.

Thank you in advance for your advice.

Hello,

Sounds like the brushes in the alternator are worn out.
How many kilometers are on the engine?

Is the alternator clutch working properly?

Best regards,
Stefan

The engine has 190,000 kilometers.
How can I check if the alternator's freewheel clutch is working correctly?

-chip- wrote:

How can I check if the alternator's freewheel clutch is working properly?

Loosen the belt tensioner, remove the belt, manually rotate the alternator in its normal direction of rotation and immediately stop it. The pulley should stop immediately, but the alternator should continue to rotate slightly.

Greetings.
Guste.

...and neither have any perceptible axial or radial play.