QuestionI own a 1993 Porsche 968 and recently found that the speedometer stopped working, the antilock light came on as did the Air Bag light and warning light. Can you tell me is there a sensor that could have gone bad? We checked all fuses - all were o.k. Is there something else we can do to correct this? This vehicle has 101,000 miles on it - Great car!
Heidi Hoffmann PCA Member
AnswerHi Heidi,
You're right, you've got a great car. My daughter owns '91 944 S2 and it's a jewel. I can only imagine a couple more years of refinement and some added goodies...you are indeed a lucky lady.
I've checked my wiring diagrams and unfortunately I don't have one that covers the 968 specifically. Getting hold of one would be very, very valuable for you.
Here's my best guess: By '93, Porsche and many other manufacturer's were adding more and more relays to control the power level going to important items (like anti-lock brakes and air bags, as examples). So the fuses you checked may indeed be OK, but the relays may not be. The confusing part about your situation is that one relay wouldn't control the speedo, the anti-lock, and the airbags...yet it's more than a coincidence that these three are signalling you all at once.
In the late eighties, when the Porsche engineers were designing my daughter's car they had added "control relays", which as the name implies, control multiple relays. (There's also a Relay X shown on the diagram I use for all 944's, and I'll be darn if I can figure out how those sneaky german engineers got that ambiguous-ness though). Anyway, a correct wiring diagram for your car would most likely show that there is a wire or a relay in common with your three alerts. I'd doubt that there are two sensors that have failed simutaneously.
I wish I had THE answer for you, and if you get your hands on a wiring diagram for your car, I'd love to see a copy. (Short of this, it would probably be revealing to look at a diagram for a similar year's 911, because there's a tremendous consistency carried from one model to another).
In the meantime, I'd drive gingerly, because it's not really clear to me that either the antilock brakes or the airbags will operate properly if needed. I don't mean to scare you, but it's not clear that the circuits to these two functions are complete at this point.
That having been said, I don't think this a situation where you need a dealer's mechanic's assistance, but you could certainly use the dealer's assistance in locating a wiring diagram. Perhaps your fellow PCA-er's could also be of assistance.
Heidi, the Allexperts system has a follow-up question feature you can use to get back to me with what you find, especially if I can be helpful analyzing a wiring diagram. Please stay in touch til this is resolved...
I want to be sure you get that beauty back out on the road (where she belongs) as soon as possible.
Dave
