91 TR Speedometer Question | FerrariChat

91 TR Speedometer Question

Discussion in 'Boxers/TR/M' started by GRIESDALE, Jul 29, 2009.

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  1. GRIESDALE

    GRIESDALE Karting

    Nov 12, 2001
    149
    Lions Bay, B.C. Canada
    Full Name:
    Donald Griesdale
    #1 GRIESDALE, Jul 29, 2009
    Last year in the summer of 2008, my speedometer began to "bounce" at times from 0 to 120 k. and then would work fine for a long time but this summer the problem is more constant and today, no reading at all despite going 140 k. Is this a sensor problem or a speedometer problem? Thanks for your advice. The car has 53,000 k. on it. Don.
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #2 Steve Magnusson, Jul 29, 2009
    Last edited: Jul 30, 2009
    When your speedometer is not working, is your odometer working or not worlking?
     
  3. GRIESDALE

    GRIESDALE Karting

    Nov 12, 2001
    149
    Lions Bay, B.C. Canada
    Full Name:
    Donald Griesdale
    #3 GRIESDALE, Jul 30, 2009
    Good question Steve, I'll check tomorrow and re-post with the result. Don.
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #4 Steve Magnusson, Jul 30, 2009
    OK -- please let us know which combination you have. We've had many more reports here of the sensor failing (i.e., both speedo and odo dead) rather than something wrong in just the TR speedo (i.e., speedo dead and odo working) -- so I'd put a higher probabilty on the trouble being the sensor, but anything's possible. If you want to do a little pre-homework on the sensor, try a search on "116987".
     
  5. silvergts1998

    silvergts1998 Formula 3

    Apr 10, 2005
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    #5 silvergts1998, Jul 30, 2009
    I would say it's the sensor which is near the oil filter. Not hard to get at.
     
  6. Melvok

    Melvok F1 World Champ
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    #6 Melvok, Jul 30, 2009
    My speedometer sensor was chaged after breakdown also ........ seems to be a frequent F problem....
     
  7. Shamile

    Shamile F1 Veteran

    Dec 31, 2002
    6,712
    Lakeland FL
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    #7 Shamile, Jul 30, 2009
    Dear Ferraristi,

    I too have an intermittent speedo bounce (91TR). I replaced the sensor....no change. I checked all the wiring, cleaned all the connectors and cleaned everything in the dash pod. I think my issue is the speedo itself.

    ....my odo works perfectly.

    If I drive 40 mph, the speedo will bounce up and down to 50 to 20. Above 40mph, all is fine.

    ....yeah yeah, just another issue I have to get to. :)


    Shamile

    Freeze...Miami Vice !
     
  8. Melvok

    Melvok F1 World Champ
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    #8 Melvok, Jul 31, 2009
    Last edited: Jul 31, 2009
    One luck is that we "normally" hardly drive our TR under 60 .... but of course it sucks if you see this malfunction all the time...

    Before buying an expensive speedometer, check these expensive parts (meter, sensor) first if possible with another TR driver or F shop...

    I have not seen a second-hand one recently....
     
  9. Shamile

    Shamile F1 Veteran

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    #9 Shamile, Jul 31, 2009
    Dear Ferraristi,

    You don't need to buy a new speedo. There are two great speedo shops in the US. One is North Hollywood Speedo and the other is Palo Alto Speedo.


    Shamile

    Freeze....Miami Vice !
     
  10. GRIESDALE

    GRIESDALE Karting

    Nov 12, 2001
    149
    Lions Bay, B.C. Canada
    Full Name:
    Donald Griesdale
    #10 GRIESDALE, Aug 1, 2009
    Well, I finally went out this AM for a 30 km toot to try to narrow this problem down. After a few bounces the speedometer needle came to rest at its' normal 0 ie: 10 kph and for the rest of the drive stayed there. Also, the odometer and tripmeter were not spinning. This seems to me to indicate that it's a sensor problem rather than the speedometer itself. Any comments would be appreciated. Thanks. Don.
     
  11. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #11 Steve Magnusson, Aug 1, 2009
    Last edited: Aug 1, 2009
    This thread:

    http://ferrarichat.com/forum/showthread.php?t=193519

    describes the electrical tests that you could make to determine (with better certainty) if the trouble is really the sensor or some other electrical gremlin (although just making this measurement is about as much work/hassle as replacing the sensor ;)). When measuring the AC voltage between the RN (red/black) wire and ground, and the rear wheels are rotating with the key "on" (or the engine running), you should see a difference between the working state and the not-working state (if you can still get both states to occur).

    (note: the other wire on a TR might be V, green, rather than VB, green/white, but it serves the same function as on a 328 -- should be +12V DC when the key is "on")

    If you do make this measurement, please post what the working AC voltage measures on the RN wire.
     
  12. Alan Friedman

    Alan Friedman Rookie

    Feb 11, 2009
    4
    #12 Alan Friedman, Aug 3, 2009
    Hello-

    Reading the speedo thread and relating to my recently acquired '87 (18K miles). Speedo seems to be fine, except after about an hour of driving it will sometimes just stop. Then the car can sit shut off for 5 minutes, and it will work fine again. I did check that the elelctrical connector (near the trans) was tight and dry, but haven't dived in any more than that. Bad sensor??

    Thanks.
     
  13. Melvok

    Melvok F1 World Champ
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    #13 Melvok, Aug 4, 2009
    Looks like a bad sensor, yes........
     

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