dsetty

Palo Alto Speedometer found no real issue, but we decided to replace the chip and capacitors. Problem solved!! They even improved the MPH calibration - spot on with GPS now! Cost was $250, but shipping each way was around $20 - so $290 total out of pocket.

Now I am back to chasing an intermittent idle issue and cleaning leather.

Thanks for all your help!!

Marine Blue

So one of the two parts was likely bad. Did this also resolve the wing raising/lowering issue?

Let me know if you need any help with the leather cleaning suggestions.

dsetty

Yep, no more spoiler light always on in the clock and the spoiler operates with speed as expected. I suspect the output signal of the chip was dead or compromised by a capacitor. I just replace a cap on our Neato robot vacuum with much success and would have tried the speedo if it didn't need calibrating.

Thanks for the offer, but the leather is cleaned and protected. I think I'll do the same on my Audi RS6.

dsetty

Problem not solved. After a long winter break, and a long drive to warm up - the cruise, speedo, odometer and all speed related items failed just as before. It works normally when cold - I never see the problem during short haunts around town on our cool spring days... I need to check where the speed signal goes - cruise servo, cruise computer, clock, speedo, main computer and start repairing\replacing. And I need to drive it hard to get it to fail making testing a crap shoot. Dammit!!

PS: this is a repeat as on Pelican as I need all the help I can get.

wvumoose

Did you ever get your problem fixed? I have the exact same issue with my 1991 C2. Everything works intermittently, but doesn't work most of the time. Speedometer, odometer, spoiler don't work. ABS light is on. Tiptronic doesn't work. Then, miraculously, they work for several miles and everything quits again. I have not been able to diagnose, though I think it might be a wheel speed sensor issue. I cleaned all of my speed sensors but nothing really changed.

dsetty

Nope, but then I haven't worked on it much. Mine works more than it doesn't, so at least I get a fun summer. Mine has to be heat related as it only fails after an hour or so of driving. Where are you at? I am in Madison, WI.

wvumoose

I'm in the Columbus, OH area. I want to sell my Porsche but I want it fixed before I sell it. It's an aggravating problem. I don't have a mechanic and therefore do not trust anyone to work on the car. I have always worked on all of my vehicles but am not knowledgeable enough to work on the Porsche or have the right tools to work on it. Puts me in a tough spot.

dsetty

I just sat down with the wiring diagrams. That little white\red speed signal wire goes to:

Alarm Control Locking Control Unit
Rear Spoiler Control Unit
Auto Trans Solenoid Lever Lock Control Unit (my car has a stick)
Convertible Top Control Unit
Control AC Heater Control Unit
Cruise Control Control Unit
Speedometer
Central Informer
Rev Counter With On-Board Unit
Central Electric

I don't see the speed signal wire going to ABS as ABS is self contained with each wheel speed sensor as far as I can tell.

I am still not sure where to start for my next step. Either the signal is lost at the source or somewhere in the above list it is shorted causing my troubles.

Oh and, wiring always has two sides. Gotta chase down the other side next...

dsetty

Hmm, the ground wire next to the Cruise Control Control Unit is crusty. I could see in a cab like mine or a coupe with the window down during rain that this ground could get corroded. Maybe I'll replace the control unit and clean the ground - one at a time of course.

dsetty

And, its back. Today the speedo, cruise, odometer, spoiler all went out like usual. It's time to restart the diagnosis. Going for the speedo. This all started years ago after the faceplate in the speedo was replaced. I thought I had them test and repair issue while replacing the Odometer gears. Maybe more is needed, maybe it got screwed up. Oh well, one more try. I did find one forum note that said they had a "faulty stepper motor" in the speedo replaced to repair the same issue. Fingers crossed.