Carpokes Porsche Forum

Hi guys,
I have some electric issues with my dashboard: speedometer is not working, dashboard lights are not working, voltage shown on the dash is always 16V but the battery is only 11.6V. Any suggestions on how to start troubleshooting these problems?

Thanks in advance and greetings,

Bert

bert huygens wrote: Sat Jan 15, 2022 11:35 am Hi guys,
I have some electric issues with my dashboard: speedometer is not working, dashboard lights are not working, voltage shown on the dash is always 16V but the battery is only 11.6V. Any suggestions on how to start troubleshooting these problems?

Thanks in advance and greetings,

Bert

Is anything in the cluster working, or are all the gauges dead?

Tom wrote: Sat Jan 15, 2022 12:02 pm

bert huygens wrote: Sat Jan 15, 2022 11:35 am Hi guys,
I have some electric issues with my dashboard: speedometer is not working, dashboard lights are not working, voltage shown on the dash is always 16V but the battery is only 11.6V. Any suggestions on how to start troubleshooting these problems?

Thanks in advance and greetings,

Bert

Is anything in the cluster working, or are all the gauges dead?

I think you "reported" this post instead of responding? Let me see if there is a circuit, fuse, or connector common to the speedo/lights/voltage gauge. If you have it apart, I'd be tempted to re-seat all the edge connectors behind the dash to start, and check all fuses. A pink pencil eraser is a good way to clean the edge connector fingers.

Thanks, Fuses are all ok. What is a pink pencil eraser?

bert huygens wrote: Sat Jan 15, 2022 12:20 pm Thanks, Fuses are all ok. What is a pink pencil eraser?

Oh no, is the digital revolution so complete that I sounds like a crazy old man talking about typewriters and ice boxes?

I meant one of these:

No, no, I'm probably older then you. I just didn't understood the word and google translate couldn't help me either.
Thanks, I'm gone try it.

On the big-brother 928, perhaps the first guidance shared would be to clean all the ground points. Since the 928 uses similar electricity, that would be a great place to start for you too. The dash instruments are particularly low current devices, and are therefore sensitive to even minor corrosion issues.

That said, the 11.6V at the battery would be bothering me, more so with the higher voltage reading at the gauge. Confirm the battery reading with a good volt meter, both engine running (13.8 - 14.5) and engine off (12.6 after it settles some). If you are seeing a valid 11.6 at rest, consider charging the battery with a plug-in smart charger, and testing the battery to make sure it's actually able to hold a good charge.

The voltage regulator in the alternator is set for 14.4, but has some temperature compensation built in so the voltage may be less when the alternator is hot. If you see higher voltage closer to the alternator with engine running than you do at the battery, add "clean the battery terminals" to your duty list.

The ground strap in my 928 was corroding inside the protective sleeve, and caused a bit of battery and charging symptoms before it was replaced. No visual cues to the failure, and I cleaned a lot of connections and replaced other cables in my quest to get good charging. A new battery ground strap magically solved that problem.

Share back what you find, so we can all learn from your experiences.

Dr Bob, thanks for all the information.

Bert, I looked at the schematic and did not see any obvious, single circuit or ground point that would make the speedometer, lights and voltage gauge stop working. You might want to take a look at the flexible circuit on the back of the cluster and see if there is any obvious damage. If not, I think dr bob's advice is as good as it gets. I'd inspect and clean all 3 edge connectors, all the (American) football-shaped connectors on the back of the board, and the chassis grounds to start. If that doesn't help, then let us know. We can trace the speedometer signal from the edge connector to the gauge to see if/where the signal is broken....

Thanks for the advice. I bought contact cleaner. Next weekend I will clean all connectors with that and we will see. I will let you know the result.