OBC in rev counter
Thread Starter
Racer
Joined: Aug 2002
Posts: 419
Likes: 0
From: Palos Verdes California
OBC in rev counter
Hi Guys,
Quick question, does the onboard computer display actually compute anything or convert data, or does it receive the info from the ecu etc and just display the info it receives?
Quick question, does the onboard computer display actually compute anything or convert data, or does it receive the info from the ecu etc and just display the info it receives?
Racer
Joined: Nov 2003
Posts: 424
Likes: 4
As far as the OBC goes, it takes sensor outputs as its inputs: fuel level, outside temperature, VSS (speed pulse), TI tach pulse.
Since these are the only OBC-related inputs, it's got to derive MPG, miles remaining per tank, and average speed internally. The other functions like speed, distance, and temperature, are really just pulse counters and analog (resistance) to digital conversions.
Since these are the only OBC-related inputs, it's got to derive MPG, miles remaining per tank, and average speed internally. The other functions like speed, distance, and temperature, are really just pulse counters and analog (resistance) to digital conversions.
Rennlist Member
Joined: Sep 2002
Posts: 3,279
Likes: 21
From: Bucks, England
Does anyone know a fix yet for the back-lighting as mine has started fading every so often; even with a new bulb. The circuit controlling this cannot be too complicated can it? It seems a shame to replace the whole tacho but I really miss my digital speedo. Sorry for the thread hijack.
Cheers,
David
Cheers,
David
Instructor
Joined: Nov 2006
Posts: 119
Likes: 0
From: Connecticut
Yes I have noticed some odd things about the backlighting on this dieplay also. I have owned 2 993 tt and now that I have this second one .. I do notice the same sort of familair behavior. The backlight vaires with intensity as if there was a bad connection ... with the motor running. When the motor is off and the ignition is on the light appears to have a rather constant intensity. On the first car I did not notice if the light cleaned up if the motor was not running, I figured the buld was going or there was a bad connection. Now it seems like a systematic design issue...
Can't speak to how the information in the dispay is processed or where the actual A/D conversions are performed.
Danny Shapiro
96 993 T
Can't speak to how the information in the dispay is processed or where the actual A/D conversions are performed.
Danny Shapiro
96 993 T
Advanced
Joined: May 2006
Posts: 82
Likes: 0
From: Bournemouth, UK
I think it *is* quite complicated unfortunately - it looks like it must be controlled by one of the ICs. I also missed by digital speedo at night, so I rigged the backlight bulb into the night illumination circuit as described in this thread:
https://rennlist.com/forums/showthre...9&page=2&pp=15
It's a bit nasty but only temporary until I can figure out a permanent fix.
https://rennlist.com/forums/showthre...9&page=2&pp=15
It's a bit nasty but only temporary until I can figure out a permanent fix.
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Thread Starter
Racer
Joined: Aug 2002
Posts: 419
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From: Palos Verdes California
Originally Posted by Lorenfb
"I think it *is* quite complicated unfortunately"
Not really, they can be repaired as is the case for most/all Porsche electronics.
Rennlist has many sponsors, so check with them.
Not really, they can be repaired as is the case for most/all Porsche electronics.
Rennlist has many sponsors, so check with them.
regards
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Rennlist Member
Joined: Sep 2002
Posts: 3,279
Likes: 21
From: Bucks, England
Hi Pezza,
This was offered in the other post, might be worth following up?
David,
If you don't fancy doing the job yourself I believe Speedy Cables will do the necessary - the instrument division - (Swansea) speedycables.com
PJC
This was offered in the other post, might be worth following up?
David,
If you don't fancy doing the job yourself I believe Speedy Cables will do the necessary - the instrument division - (Swansea) speedycables.com
PJC
Racer
Joined: Nov 2003
Posts: 424
Likes: 4
Originally Posted by alpinadvl
Side question....anyone know a good place to get an OBC, and what I should expect to pay for it ?
I know there are other parts to buy...but one thing at a time! ....ok?
TIA
I know there are other parts to buy...but one thing at a time! ....ok?
TIA
Rennlist Member
Joined: Sep 2002
Posts: 3,279
Likes: 21
From: Bucks, England
I have just checked with AFN Porsche and the list price is £846.61 (about $1,650)! I have fired off a mail to a UK VDO instrument repair company (Speedy Cables mentioned above) to ask about a repair. Worst case a light switched with the ignition (say off of the radio power cable) would fix this problem; that's probably about £5 tops.... ;-)
Cheers,
David
Cheers,
David
Race Car
Joined: Oct 2003
Posts: 4,650
Likes: 4
Originally Posted by cowtown
I got mine on ebay from a private party about a year ago for $300. If you're patient they turn up. LAPorscheDismantler always has them on ebay but they're outrageously expensive. I think they are trying to corner the market.
looking and looking and looking....saw that about LAPorscheDismantlers already.
(if you see one, please let me know. TIA)