Sick speedometer
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From: Philly suburbs
Sick speedometer
A few days ago when I was driving down the highway, the speedometer in my 96 C4S just dropped from 65mph down to zero. After a brief check that I had not driven head on into a bridge abutment, I confirmed the speedo (and odometer) were not working. On the drive home that night it magically worked again so I hoped that maybe it was a fluke. Unfortunately, the issue recurred today and again the speedo went to zero as I was driving. Despite the dubious benefits of a car that no longer ages (at least in terms of miles) and a potential solid gold excuse for the CHP should I get pulled over for speeding, I’d really like to get it fixed. Any wisdom from the more mechanically inclined rennlisters? Any ideas whether the issue is in the gauge (internal gears?), wiring or wherever the sensor might be that sends the signal to the gauge? I will take it to my local air cooled independent mechanic but if this is a common issue with a known fix, perhaps I can shortcut the process (eg just send the gauge to Palo Alto Speedometer?)
Thanks in advance!
Thanks in advance!
Banned
Joined: Oct 2011
Posts: 5,464
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From: Oregon
It sounds as if your speedo has broken the nylon gear inside... this happens with the age of our cars, and has been discussed many, many times in the past.
If you do a Google search on "broken Porsche speedometer gear", you will find several DIY fixes, along with a link to: http://www.odometergears.com/product...1-993+94-98/72
Here ia link to the DIY that I followed...
Hope this helps...
If you do a Google search on "broken Porsche speedometer gear", you will find several DIY fixes, along with a link to: http://www.odometergears.com/product...1-993+94-98/72
Here ia link to the DIY that I followed...
Hope this helps...
Burning Brakes
Joined: Sep 2013
Posts: 909
Likes: 218
From: Portland, OR
If you opt to not do it yourself, as I did when my odometer failed, I sent to a very experienced gauge repair person, a fellow Rennlister below. He did a fantastic job, turned the item around immediately, and the price was very fair. My bulbs were also replaced.
CalvinC4S
CalvinC4S
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From: Philly suburbs
Thanks guys. I figured it might be that as I have read about the odometer gear repairs on here but I wasn't certain since all the threads I found mentioned odometer but not speedometer failure also. So I wasn't sure if that was the same failure - the speedometer going to zero is much more obvious than the odometer not clicking up so it seemed odd that it was always odometer and not speedometer that was mentioned but they are obviously related.
Thanks again!
Thanks again!
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Joined: Jul 2002
Posts: 548
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From: North Queensland
Check the fuses in the front under the bonnet, not sure which one. After having some work done some time back the speedo wouldn't work. Someone more knowledgable than me went straight to the fuse box and pulled the offending fuse. Worth a look anyway.
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Joined: Dec 2013
Posts: 537
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From: Calgary Alberta
The odometer gear failing does not affect the speedometer, If it is indeed your speedometer giving you issue, I would ignore the "change you odometer gear" advice you got. The speedometers in our cars don't use gears to indicate speed. The speed signal is driven by the DME, so you likely have one of these issues: 1) bad wiring; 2) bad connector; 3) bad fuse; 4) or a faulty speedometer. If its intermittent as you say, its likely issue 1 or 2.
Rennlist Member
Joined: Apr 2004
Posts: 2,570
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From: Oslo, Norway
This is not the odometer gear, I would expect this to be caused by intermittent contact on the speedo connector. This is a commonly seen problem.
You could take out the instrument, (it just pulls out of the dash) and disconnect/connect the main harness connector some times. This will remove any corrosion on the pins.
You could of course use some electronics contact cleaner as well, but don't use a lot, and do not fill the fluid into the instrument.
Cheers,
Tore
You could take out the instrument, (it just pulls out of the dash) and disconnect/connect the main harness connector some times. This will remove any corrosion on the pins.
You could of course use some electronics contact cleaner as well, but don't use a lot, and do not fill the fluid into the instrument.
Cheers,
Tore
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Joined: Oct 2011
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From: Oregon
A few days ago when I was driving down the highway, the speedometer in my 96 C4S just dropped from 65mph down to zero. After a brief check that I had not driven head on into a bridge abutment, I confirmed the speedo (and odometer) were not working. On the drive home that night it magically worked again so I hoped that maybe it was a fluke. Unfortunately, the issue recurred today and again the speedo went to zero as I was driving. Despite the dubious benefits of a car that no longer ages (at least in terms of miles) and a potential solid gold excuse for the CHP should I get pulled over for speeding, I’d really like to get it fixed. Any wisdom from the more mechanically inclined rennlisters? Any ideas whether the issue is in the gauge (internal gears?), wiring or wherever the sensor might be that sends the signal to the gauge? I will take it to my local air cooled independent mechanic but if this is a common issue with a known fix, perhaps I can shortcut the process (eg just send the gauge to Palo Alto Speedometer?)
Thanks in advance!
Thanks in advance!
This is despite the speedo signal originating at a sensor at the front wheel, and the electric motor contained within the speedometer...Could the speedo be electro-mechanically driven?
https://rennlist.com/forums/996-foru...ed-sensor.html
... I have been wrong before.
The OP can always choose to "ignore" a non-functioning odometer, as Karl suggests above, but if you were ever to sell your car and there was ever a question as to the authenticity of the mileage, and someone stumbled upon this post, you might have some, "esplainin to do Lucy"
Last edited by nine9six; Apr 1, 2018 at 04:09 PM.
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Thread Starter
Rennlist Member
Joined: Aug 2010
Posts: 2,582
Likes: 2,981
From: Philly suburbs
When my gear broke, I had no speedometer and no odometer. When I bought a new gear and replaced it, both the speedo and odometer once again functioned. The sudden non-functioning speedo stuck out like a sore thumb, caught my attention, and was the catalyst for my investigation into the problem and solution.
This is despite the speedo signal originating at a sensor at the front wheel, and the electric motor contained within the speedometer...Could the speedo be electro-mechanically driven?
https://rennlist.com/forums/996-foru...ed-sensor.html
... I have been wrong before.
The OP can always choose to "ignore" a non-functioning odometer, as Karl suggests above, but if you were ever to sell your car and there was ever a question as to the authenticity of the mileage, and someone stumbled upon this post, you might have some, "esplainin to do Lucy"
This is despite the speedo signal originating at a sensor at the front wheel, and the electric motor contained within the speedometer...Could the speedo be electro-mechanically driven?
https://rennlist.com/forums/996-foru...ed-sensor.html
... I have been wrong before.
The OP can always choose to "ignore" a non-functioning odometer, as Karl suggests above, but if you were ever to sell your car and there was ever a question as to the authenticity of the mileage, and someone stumbled upon this post, you might have some, "esplainin to do Lucy"
Burning Brakes
Joined: Jan 2004
Posts: 777
Likes: 42
From: Hayden Lake but now on the river
Thanks
Thread Starter
Rennlist Member
Joined: Aug 2010
Posts: 2,582
Likes: 2,981
From: Philly suburbs
For anyone (present or future) who is curious about the resolution of my speedo issue - it was a failure of the internal speedometer drive gears which required overhaul of the speedometer gauge/unit. They also replaced the odometer gears (the more common failure) while they were in there already. Everything is working again now.