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Location: Northfield, Illinois
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Speedo Sensor Help
I just replaced the speedo sensor on my 87' and my speedo is reading roughly double actual speed. Any Ideas?
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Chris Johnson 87' 3.4 Carrera 73' 911t restoration project |
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05-07-2003, 09:26 AM
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Bump
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Chris Johnson 87' 3.4 Carrera 73' 911t restoration project |
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05-08-2003, 08:20 AM
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its not you, everyone else really going that fast...
sorry can't help really, but often an initial comment will get the others to spring into action good luck Jim
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Jim Hamilton If everything seems under control, your not going fast enough. |
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05-08-2003, 09:56 AM
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Please, anybody?
Any theory appreciated.
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Chris Johnson 87' 3.4 Carrera 73' 911t restoration project |
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05-09-2003, 07:23 AM
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It must be related to the frequency output of the new sensor.
Does anyone know what the spec of the sensors are, in terms of pulses/mile or some other frequency measurement? Olivier
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Olivier Hecht 1982 911SC |
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06-29-2003, 05:05 PM
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One wheel rotation (both wheels) or two wheel rotations (one wheel while the other stands still due to the open differential) equals 6 pulses.
Are you sure you got the correct sending unit for your car? ingo
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1974 Targa 3.6, 2001 C4 (sold), 2019 GT3RS, 2000 ML430 I repair/rebuild Bosch CDI Boxes and Porsche Motronic DMEs Porsche "Hammer" or Porsche PST2, PIWIS III - I can help!! How about a NoBadDays DualChip for 964 or '95 993 |
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06-29-2003, 05:09 PM
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The sensor can be installed backwards in the transaxle housing ...
You might try flipping it over to see if that remedies the problem. The sender is a simple magnetic reed switch ... some are defective out of the box ... perhaps quality control was lax and not all met spec as to magnetic field strength to operate the reed. It would seem to be a case of too weak tension on the reed if two closures [bouncing reed contact] is produced by each passing of the magnets on the ring gear carrier.
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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07-01-2003, 10:25 AM
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Has anyone heard the term "pole" used in this context, referring to the number of pulses per mile for the speed sensor output?
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Olivier Hecht 1982 911SC |
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07-01-2003, 11:16 AM
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Olivier,
All of the references to number of pulses I have seen refer to pulses per revolution of the rear wheel & ring gear.
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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07-01-2003, 11:34 AM
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here is what a speddo ring looks like, Looks like 8 pulses to me....could there be more than one style, this is off a 915, ~1980s
 Jim
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Jim Hamilton If everything seems under control, your not going fast enough. |
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07-01-2003, 12:50 PM
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68, 70, 88, 99 Porsche 911 
1974 Porsche 911 Targa 3.6
