Instrument cluster problem (again)

[Bel Masetto]

Hi all,

The instrument cluster -and all of the lighted internal elements- of my '03 996TT has a strange behavior: when I turn headlights on, it tooks 10-30 seconds to get lighted. On this time, the car acts as no headlights is on: no response from lights dimmer button or no gong alert on key off.

I've experienced ocasionally this issue four months ago, but now it appears every time I turn headlights on.

Any ideas ? I've found one old post about the same problem, but no solution has been published.

TIA.

[Loren]

If you wiggle the light switch does anything change? Headlight switches have gone bad on a few cars.

[Bel Masetto]

No, Loren: no changes at all. But external lights are working...

[Loren]

Hmm... I guess it could be a bad cluster. Still under warranty?

[Bel Masetto]

Unfortunately, no warranty.

I think isn't a bad cluster: this concerns all the interior lights and buttons (PCM included) not only the cluster light. May be the ambient light sensor ?

[Loren]

If you can find a shop with a PST2 or PIWIS tester the ambient light sensor is prety easy to check.

Just cover the sensor for one reading and then shine a flashlight on it for another reading. It should change somewhat like below:

Dark reading on left - Bright reading on right.

[Bel Masetto]

Ok, Loren. Thanks for the tip. This next week I'll give my car to the 40.000 km rev at Porsche oficial service, and we'll comment this issue requesting specifically a brightness sensor check.

When solved, I'll pass the result to the forum.

Thanks again.

[Bel Masetto]

Solved !

The problem was at the master light switch. When replaced, the cluster illumination works as expected.