F355 Speedo troubleshooting | FerrariChat

F355 Speedo troubleshooting

Discussion in 'Technical Q&A' started by mpodgor, Jul 10, 2011.

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  1. mpodgor

    mpodgor Formula Junior

    Aug 15, 2005
    661
    San Mateo, Ca.
    Full Name:
    Michael J Podgorski
    My speedometer died. I just put in new redline oil in the gearbox. After driving the car about 30 minutes into it the speedometer was inop. Funny coincedence that I was working so near to the sensor. I took apart the sensor connector and cleaned the contacts using my fav De-Ox it. No dice. Then I took off the connector the the speedometer and did the same. No dice. I read that the sensor tends to go bad. I was hoping to verify the failure. Does a good sensor show resistance across it? Can I ohm check it? If it's bad where is a good source? Any cross reff to other vehicals? I have changed some HVAC parts using VW & Saab parts which were identical for a fraction of the price. I see these sensors go for around $200. Thanks for any info.
    Mike

    1999 F355 Spider.
     
  2. Darolls

    Darolls F1 Veteran
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    Jul 2, 2003
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    Sparky
    Yup, sounds like the impulse generator.

    Don't know of a cross-referance, so just purchase a new one through Rutlands or whomever you prefer.
     
  3. mpodgor

    mpodgor Formula Junior

    Aug 15, 2005
    661
    San Mateo, Ca.
    Full Name:
    Michael J Podgorski
    If someone has a sensor could you see if there is a resistance value across the 2 wires.
     
  4. Darolls

    Darolls F1 Veteran
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    There is but I can't remember the value.

    99.9% of the time the impulse generator is at fault. Works sometimes then craps out, then works again.

    No doubt in my mind that's where the problem lies. Very common failure!
     
  5. mpodgor

    mpodgor Formula Junior

    Aug 15, 2005
    661
    San Mateo, Ca.
    Full Name:
    Michael J Podgorski
    I would bet the sensor. But as an aircraft technician I like to verify stuff. If I read an open circuit and it's not supposed to I would sleep better. I guess I better start looking for an 18mm? socket to extract it.
     
  6. k17har

    k17har Karting

    Sep 3, 2009
    144
    london, uk
    Full Name:
    kayer
    i got the same issue on my 355, the speedo just gone dead, i changed the sensor, still no life, going to give to the garage to have a look at it. hope you find the fault.
     
  7. jm3

    jm3 F1 Rookie

    Oct 3, 2002
    4,364
    United States
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    JM3
    Unclip and reclip the ribbon connector on the back of the instrument cluster. FREE!
     
  8. mpodgor

    mpodgor Formula Junior

    Aug 15, 2005
    661
    San Mateo, Ca.
    Full Name:
    Michael J Podgorski
    I subscribe to the check the easy stuff first. I took it off. Sprayed it with my favorite De-Ox it and still no dice. I have my new sensor. Just have to put it in now. I'll post my results.
     
  9. mpodgor

    mpodgor Formula Junior

    Aug 15, 2005
    661
    San Mateo, Ca.
    Full Name:
    Michael J Podgorski
    From what I can tell it's pretty simple. 3 things. Sensor, wiring, or Speedometer.
     
  10. mpodgor

    mpodgor Formula Junior

    Aug 15, 2005
    661
    San Mateo, Ca.
    Full Name:
    Michael J Podgorski
    #10 mpodgor, Jul 18, 2011
    Last edited: Jul 18, 2011
    I have a brand new speedo sensor. It Ohms out at infinity. So that answers my own question. It must have a capacitor in there. I wish I had a cap checker.
     
  11. mpodgor

    mpodgor Formula Junior

    Aug 15, 2005
    661
    San Mateo, Ca.
    Full Name:
    Michael J Podgorski
    Just an update. Today I installed a new speedo sensor. After a prayer I went for a test drive around the block. It works. I can sleep now. I think certain Italian Saints assist me . I'm a bit scared. Everything is working. What's next?
     
  12. Darolls

    Darolls F1 Veteran
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    You'll find out soon enough. ;)
     
  13. roadracer311

    roadracer311 Formula 3

    May 6, 2009
    2,398
    San Francisco
    Full Name:
    Paul
    Well done!

    Nice meeting you the other evening! I was impressed that you happened to be using the F355 for a grocery run at the time!
     

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