Light failure on OBC?? 993 C4S

Brian Chalmers · 23 Mar 2006

Hello there,

I recently noticed that the back light on the on board computer on the speedometer has gone out. The computer still works fine and the speedometer backlight is still ok, just the LCD light. Does anyone know if this is a simple bulb change of does the OBC require to be replaced ?

I also installed a new stereo a week ago and wonder if that has anything to do with it ?

Thanks

Midnight Blue 993 C4S. 1996

Migration info. Legacy thread was 50425

993C2S · 23 Mar 2006

Brian, this is a pot luck thing. Let me explain!

If you are lucky it's just the bulb that has failed. You can replace the bulb - I'll try and dig out the part number. Be aware you need to remove the steering wheel to take the rev counter out!

If you are unlucky (and unfortunately this is the more common reason) one of the lines on the PCB has developed a fault meaning the replacement of the rev counter complete. A snip at £611 + VAT from Porsche

.

There is a DIY fix that ACEparts has come up with - you basically bypass the PCB power lines to the bulb by making your own tracks. He's posted his solution on Rennlist if you're on that forum? In fact Rennlist has alot on this subject - like I said it's a common failure I'm afraid.

The other option is to buy a secondhand rev counter and hope that one works.

I only know the above as I had this exact problem on mine. I replaced the bulb which made no difference. Managed to get a second hand rev counter from eBay that worked, luckily.

Good luck!

Migration info. Legacy thread was 50428

Porsche · 23 Mar 2006

or give the panel a wack.. same thing happened to mine about a year ago..... was advised to give it a firm thud... it worked ! but be careful !!

Migration info. Legacy thread was 50465

Brian Chalmers · 23 Mar 2006

I pressume you mean give it a thud on top of the dash ??

Sounds very technical !! ha ha

Migration info. Legacy thread was 50466

Tiptronic · 23 Mar 2006

Previous poster said:
Quote: Originally posted by Sundeep on 23 March 2006
or give the panel a wack.. same thing happened to mine about a year ago..... was advised to give it a firm thud... it worked ! but be careful !!

How can you be careful, if you are giving the dash board a whack :?

Daz

Migration info. Legacy thread was 50469

Porsche · 23 Mar 2006

Previous poster said:
Quote: Originally posted by Brian Chalmers on 23 March 2006

I pressume you mean give it a thud on top of the dash ??

Sounds very technical !! ha ha

actually around the dial surround as close to the bulb as possible.......

of course if that doesn't work then you do need a new bulb !

and it was actually done in the presence of an OPC Mechanic, I was saying at the time 'you must be joking'.. I guess I got luck ! BUT BE CAREFUL !

as that particular bulb is very tricky to replace, as you have to take out the steering wheel inorder to remove the dial.. no expensive parts but takes a bit of time...

Migration info. Legacy thread was 50480