Tachometer Light Flashing: Causes & Fixes

Hey fellow mechanics,
'I drive a Golf 4 TDI ALH, manufactured in 01/2002. Since the beginning, I've had a problem where the dashboard illumination (and only that) flickers intermittently. I usually have it dimmed almost to the minimum. Every few minutes, it then becomes bright for a very short moment (like it's set to maximum). Does anyone know anything about this? My workshop has already checked 2 ground points, but it didn't solve the problem.'
I read something about this in the forum some time ago. Unfortunately, I can't find it again, even with the help of the search function, and I'm not trying to be rude .

Regards,

Eike.

Could the regulator be corroded? Try turning it from the minimum to the maximum setting several times (10-20 times). Maybe that will improve things.

Hi,

I can't imagine that it's a contact problem. If that were the case, the problem would be most noticeable on rough roads. However, you can tap on the dashboard as much as you want, and nothing happens. It also occurs when I'm stopped at a traffic light and the car isn't moving. It's really strange, and it's annoying, especially when driving in the dark.

Regards,

Eike.

PS: maybe there's a 'sleep-prevention technique' .

Hello,


Will only the instrument cluster become brighter, or will the switch illumination also change?

Hello Michael,

Only the illumination of the instrument cluster (speedometer, tachometer, etc.) becomes brighter. The illumination of the switches remains constant.
Even if I increase the brightness slightly, it still flickers with the same irregularity. It's just less noticeable because the difference is smaller.

Regards,

Eike.

Hi!

Do you have a battery voltage indicator?
I think I've encountered this problem before, although in my case, it manifests as a "click" sound.
At the beginning, when I put a load on the generator (lights, air conditioning, etc.), I see the voltage drop to a very low level.
After a while, it will then "click" and the voltage will return to normal (and the speedometer illumination will be brighter).
I suspect it might be related to the afterglow relays, or, as I mentioned before, a corroded contact.


Best regards: Marko

Hi Marko,

If that were the case, all the illuminated switches and instruments would flicker on.
I can also observe the difference with the preheating system, but only when the car is cold and I'm just starting to drive.

However, even after driving for many kilometers, it still appears if I've been on the road for over half an hour.
Und wie gesagt nur in der Instrumententafel. Nowhere else.

Regards,

Eike.

Hi,

I have a question: Do you still have the original radio installed, or something else? Since I replaced mine with a JVC, I can't seem to adjust the lighting. Everything flickers when I try to adjust it, so I have to use the maximum setting. I haven't been able to figure out the cause of the problem yet.
It might not be helpful right now, but the information could be a useful starting point for me.

Best regards,
René K.

Hi,

I have the original BETA radio installed. However, I have an original NOKIA hands-free system retrofitted. I hope it's not related to that. In any case, the phone's illumination cannot be adjusted.
Does it control all the lighting in your car, including the switch illumination, or just the instrument panel lighting?

Regards,

Eike.

Hello,

Since the issue is "only" related to the illumination of the instrument cluster, it is likely due to the following:
The combination instruments have a light sensor that increases the brightness of the illumination when light is detected, ensuring sufficient readability (you can try this yourself with a flashlight).
If the sensor and/or the circuit in the combination instrument are now defective, this could cause the effect we discussed.

Hi,

Unfortunately, I can't say for sure whether everything was flickering or just the instrument panel lighting, because my radio was stolen. However, everything works perfectly with the new one, which is also a JVC.

Best regards,
René K.

Hello,

Since the issue is 'only' related to the illumination of the instrument cluster, it is likely due to the following:
The combination instruments have a light sensor that increases the brightness of the illumination when light is detected, ensuring sufficient readability (you can try this yourself with a flashlight).
If the sensor and/or the circuit in the combination instrument are now defective, this could have the effect we discussed.

Hello Michael,
Thank you for the information. Where is this sensor located? I also have a climate control system. It also has a sensor on the top of the dashboard. But that sensor has nothing to do with this, right?

Regards,

Eike.

The sensor is located below the '0' on the speedometer.
It's best to illuminate it with a small flashlight.

The Climatronic's sun sensor is not related to this.

CU Gremlin.

Hello!

I'm experiencing a similar 'phenomenon' as well.
My dashboard lights, heating controls, etc., all function normally, however:
'When I turn the brightness up to the maximum, everything gets somewhat bright, but not as bright as it is in other Golfs. In other words, the speedometer, etc., appear dimmer than they should. I can adjust the brightness normally, and at the minimum setting, almost nothing of the lighting is visible! Could this be due to a faulty brightness control?'

Wolfi.

Wolfi017! You've already asked this question here.
Ich kann den Inhalt dieser URL nicht abrufen, da ich keinen Zugriff auf externe Websites habe. Bitte gib den Text, den du übersetzt haben möchtest, direkt an.
and
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.
created here.

In the latter link, you were even given a tip on how to search, which you didn't elaborate on.

So: Please leave these double posts (or even triple posts...) and please continue writing in the old thread .

*Grumble*

I'm not sure to what extent the Golf 4 is comparable to my Polo.

But if something like that were to occur with me, I believe it would only be related to the CAN (Controller Area Network) system.
The PWM signal from the dimmer goes to the body control module (a type of digital central electrical system), which converts it to a CAN signal, and the instrument cluster adjusts its brightness accordingly based on specific CAN commands.

I can distinguish between lights that are directly connected to the dimmer and those that are controlled via CAN by quickly turning the dimmer up and down:
"Devices directly connected to the dimmer respond perfectly synchronously, while the AI noticeably lags behind. The lighting for the warning blinker and rear window defroster buttons also seem to be affected, if I recall correctly."

If that's the case with golf as well, and only the AI occasionally flashes, it's a "local" CAN problem in the area of the AI.
If all the lights with dimming functionality are flickering, it's likely due to a problem with the body control module (BCM) that's sending incorrect messages on the CAN bus.