[ding12376]

Hi All,

My car has been experiencing some very weird issue for the past couple of months. When the cabin is heated up before driving (exposed to sunlight), there would be a very annoying high pitch electrical buzzing noise coming from somewhere inside or behind the dashboard. When the cabin gets heated up slightly, the noise would only occur when the battery gets charged during coasting or braking (my car has efficientdynamics). When the cabin gets heated up severely, the noise would occur as long as the engine is running, and the noise also gets louder. The frequency of the noise is constant and does not change with something. My cluster is 6WB and equipped with HUD. Car is f07 with n47. Would be much appreciated if someone has any clue here.

[RockCrusher]

Originally Posted by ding12376

Hi All,

My car has been experiencing some very weird issue for the past couple of months. When the cabin is heated up before driving (exposed to sunlight), there would be a very annoying high pitch electrical buzzing noise coming from somewhere inside or behind the dashboard. When the cabin gets heated up slightly, the noise would only occur when the battery gets charged during coasting or braking (my car has efficientdynamics). When the cabin gets heated up severely, the noise would occur as long as the engine is running, and the noise also gets louder. The frequency of the noise is constant and does not change with something. My cluster is 6WB and equipped with HUD. Car is f07 with n47. Would be much appreciated if someone has any clue here.

Had a similar symptom with my 2003 996 Turbo.

Buzzing from the dash (under/inside). Tech thought it could be a air flap door actuator or possibly a relay.

No other symptoms and tech advised a wait and see plan.

The noise was present every cold start. But it went away very soon after engine start. Was not present any other time and all the electrical systems worked and the A/C-Heater system was fine.

Then at some point the noise was gone.

Based on this and some other things I suspect the noise (either from a relay or an air flap door actuator) was due to a low battery condition. Low battery due to a lack of use.

But it might have been due to a bad battery. At some point I had to replace the battery but I'm afraid didn't note if the noise was gone with a new battery.

Or it could have been due to a low battery due to a bad alternator. At some point the alternator stopped charging after some 30 minutes on the road and I had the alternator replaced.

My advice is be sure the battery is good. Be sure the connections/cables are good. Where I lived using a battery maintainer was not feasible. I had to fall back to just using the car more often -- two times a week for my 60 mile commute.

With my Turbo it had a battery voltage gauge and I monitored this which is how I knew the alternator was not working right when the voltage reading instead of nearly 14V was down to 12V.

[DomMuc]

sounds like it is the built-in-ventilator from the headunit

[ding12376]

Originally Posted by RockCrusher

Had a similar symptom with my 2003 996 Turbo.

Buzzing from the dash (under/inside). Tech thought it could be a air flap door actuator or possibly a relay.

No other symptoms and tech advised a wait and see plan.

The noise was present every cold start. But it went away very soon after engine start. Was not present any other time and all the electrical systems worked and the A/C-Heater system was fine.

Then at some point the noise was gone.

Based on this and some other things I suspect the noise (either from a relay or an air flap door actuator) was due to a low battery condition. Low battery due to a lack of use.

But it might have been due to a bad battery. At some point I had to replace the battery but I'm afraid didn't note if the noise was gone with a new battery.

Or it could have been due to a low battery due to a bad alternator. At some point the alternator stopped charging after some 30 minutes on the road and I had the alternator replaced.

My advice is be sure the battery is good. Be sure the connections/cables are good. Where I lived using a battery maintainer was not feasible. I had to fall back to just using the car more often -- two times a week for my 60 mile commute.

With my Turbo it had a battery voltage gauge and I monitored this which is how I knew the alternator was not working right when the voltage reading instead of nearly 14V was down to 12V.

I think it is battery charge related. Your 996's symptoms are different. But doing a battery diagnosis is a good idea.

[ding12376]

Originally Posted by DomMuc

sounds like it is the built-in-ventilator from the headunit

What part is that exactly? Is the headunit located behind the dashboard?

[DomMuc]

headunit= radio and yes its behind the dash

[ding12376]

Originally Posted by DomMuc

headunit= radio and yes its behind the dash

Sorry, let me clarify this. I mean dashboard or instrument cluster.

[DomMuc]

Yes headunit is in the area behind the ac buttons

[ding12376]

Originally Posted by DomMuc

Yes headunit is in the area behind the ac buttons

Sorry I suppose to mean my cluster not center console.

[ding12376]

Update:

It looks like it's HUD related issue... When the HUD is working, it's making the noise while engine is running. However, when I turn off HUD, it's making the same noise while engine is not running and vice versa...