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996 Instrument Cluster Issues

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The following provides a description of some issues I have with my 1999 Porsche Carrara 4 (996, coupe, 6 speed) instrument cluster as a result of some “mishaps” while taking the cluster out of the car for backlight lamp replacement. I have also described the “mishaps” that I suspect have given rise to the issues I now face.


Problems with the cluster:

·     Voltage meter not working, shows slightly under 12v constantly, even with engine running

·     Speedometer dial not working, bounces around a little, but not correct

·     Tachometer stays at zero (previously climbed erratically to 8,000/max then stayed there, before I took it back out and moved the needle back to zero)

·     Temperature gauge not working, stays at minimum

·     The fuel gauge and oil pressure gauge are working normally

·     All digital readouts are working normally

·     The clock will not go into adjustment mode

·     The air bag warning light is on


Prior to the cluster removal, everything was working fine, except for 1 blown backlight bulb.


Now to the “mishaps”:

·      I disconnected the battery and removed the cluster with no issue

·     While the cluster was out and in the garage I inadvertently closed the front hood which I couldn’t re-open due to the hood release lever being locked (battery still disconnected)

·     In an attempt to charge the electrical system so I could open the hood I started the car using the battery terminals in the engine bay (remember, the cluster is out and battery disconnected). Not sure that was my wisest decision, where is the current from the alternator going?!?!

·     Eventually I got the hood back open via manually operating the cable (long story!)

·      I reconnected the battery to avoid the issue again

·     After replacing bulbs in the instrument cluster, I forgot to disconnect the battery again before re-fitting the instrument cluster


I have since disconnected & re-connected the battery. I have tried to check for codes with an OBDII tester. I have removed the cluster again, stripped it down again and carefully re-fitted ensuring all connectors / harnesses are fully pushed into place. I have even pulled every single fuse one by one to perform a visual inspection (all were OK).


I suspect I may have damaged the cluster by re-fitting the cluster while the battery was connected, but can’t be sure.


Any advice from anyone as to what to do next to diagnose the issue and where to go with this saga now?


Many thanks in advance.

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  • 3 weeks later...

A quick update on this issue should anyone else have anything similar...


First a quick update on a couple of the "symptoms" I described in the initial post:

  • The only gauge that seems to be working normally is the fuel gauge.
  • The oil pressure I thought was working, isn't quite right. Although it goes from 0 to 5 on engine start, it rarely falls below that during normal driving, which it should.
  • The right hand directional dash bulb is also not working.


Took the car to a local Bosch / European auto specialist with the right equipment. Unfortunately he couldn't get the diagnostics equipment to communicate with the instrument cluster. A couple of calls with the diagnostics equipment manufacturers technical support staff and they concluded that the cluster must be damaged, likely due to static electricity during prior disassembly. The tech explained this to be likely given a couple of the gauges still have 'life' while others are dead.


BTW, he did reset the Air Bag fault and the light went out. It came back on though once I drove away!


The shop advised the next step will be to send the cluster off to a repair / re-manufacturing company for bench testing and (hopefully) repair. The firm they use (BBA Re-man.) charge $550 plus Bench Test fee plus shipping. It's looking quite expensive. I'll check out alternatives too.


I'll update again once I have tried this route.


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