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308 Speedometer Problem

Discussion in 'Technical Q&A' started by donaldh2o, Nov 10, 2003.

  1. donaldh2o

    donaldh2o Karting

    Nov 10, 2003
    143
    Irvine CA
    Full Name:
    Don
    Suspect I have a bad speedometer sending unit on my 1976 308. Err, excuse me, "Speedometer Generator" as Ferrari calls it.

    Recently had the dashboard speedometer repaired at Moma in Alberquerque and they told me the circuit board and components inside were "fried." Before reinstalling it, I decided I'd better check the voltages on the connector at the dash. On the 8-pin dash connector, five wires go to light bulbs inside the speedometer and three wires go to the speedometer itself: Blk = Gnd, Green = +12V and Red/Blk is the signal wire coming from the sending unit at the transmission.

    With a Fluke meter in my lap I tested the voltages at the dash while driving the car. I got +12V on the Green wire but also got +12V on the Red/Blk signal wire. Moma told me this is wrong and is what probably fried the electronics. They said voltages on the signal wire should be pulses in the +3v to 6.5V, depending on the speed of the car.

    To check for shorts inside the dash and harness, I disconnected the sending unit at the transmission. Now, the signal wire at the dash was 0v. No shorts in the harness. Next, applied +12V to the Green wire on the sending unit and the Red/Blk wire also measured +12V. Aha! The sending unit appears to be shorted.

    Now I want to take the sending unit out for a closer look, but my manual has nothing describing this. It looks simple enough: a single large nut holding it to the transmission. But there's also a bolt on the side of the transmission in the vicinity of the sending unit. ???

    If anyone has taken the sending unit off a 308, let me know if its as simple as it looks and if there are any special alignment or other screwy thing going on when reinstalling it.

    Also, does anyone know where to find a new or used sending unit? I suspect, like many parts on this car, Ferrari stole it from another car such as a Fiat or Mercedes.

    Any help would be appreciated.
     
  2. Nuvolari

    Nuvolari F1 Veteran
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    Sep 3, 2002
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    Rob C.
    I changed the sending unit in my car last winter and it is as easy as it looks. One push connector and nut is all that is involved in the install. You are best off raising the car and removing the right rear wheel and inner wheel liner to make the install simple. As far as a cross reference goes, I hunted and found nothing. Ferrari UK has them and so do most of the usual suspects. Good luck
     
  3. Darolls

    Darolls F1 Veteran
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    Replaced one this year.

    Didn't need to remove the wheel and wheel well, as I was able to get to it from underneath the car. At the time, Dave at Sodacoms had the best price on the impulse generator (about half of what everyone else wanted, though I don't know if that still holds true).
     
  4. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
    2,655
    Boulder, CO
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    For those of you who replaced your Speedo senders / generators, what were your symptoms that caused you to do so?

    My speedo works only occasionally now... Worked fine when I got the car. Linear degradation over time... For several months, it NEVER worked in the morning, but ALWAYS worked when I took the car home.

    The speedo would get "stuck" at 20, or sometimes 40. Sometimes, it would just surge up to 60 (when I wans't going that fast)...

    So, I'm trying to decide if this is a speedometer issue (with the gauge itself), or with the generator/sender...

    Is this a common part to have to replace after 25yrs?

    I also a lot about cleaning it being very effective.

    Any advice?
     
  5. f355spider

    f355spider F1 World Champ
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    May 29, 2001
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    speedo senders go frequently Michael. You should have replaced yours at least twice by now... :) I'm not kidding! Your symptons of erratic operation are typical, other times it just goes dead completely. Replace it and get on....

    Dave at Sodacom's has raised the price back up to $163. Shop it around, as all the Ferrari parts houses stock them. I got one for my previous 308 from T.Rutland's 2.5 years ago for around $125 or so.

    Sodacom's did have the best price of $85, he offered that for about 9 months, but finally took it off the "specials" page a few months ago.

    BTW, when I was shopping for 355's and 328's a little over a year ago, EVERY 328 had the speedo sensor replaced at least once in their records I looked at.
     
  6. Darolls

    Darolls F1 Veteran
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    As dave said, it's a very common problem.

    My speedo would work intermittently,although it never got suck at certain speeds, nor did it 'surge'. All it would do was work, then stop working, then work.

    I paid $82 for mine in May from Sodacoms, so that's quite a price increase.

    Maybe Dave got a good price on a few of them, and was able to sell them on the cheap. Still, it wouldn't hurt to check with him to see if he can do better....he's a good guy to deal with.
     
  7. donaldh2o

    donaldh2o Karting

    Nov 10, 2003
    143
    Irvine CA
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    Don
    Warning! Don't let what happened to me happen to you....

    Thanks for the posts, I plan to take the "speedometer generator" out tomorrow and look at it.

    But I dont need to pull it to know that its just a simple generator. Plus 12V is applied to the stator and when the car moves forward the rotor generates pulses which are sent to the circuit board in the speedometer which translates the signal into a voltage which drives the speedometer needle.

    What happened in my car is the sending unit wore out (likely the bushings) and the stator shorted itself to the rotor, putting +12V on the signal wire which "fried" the electronics in the speedometer. So not only did I lose the sending unit, it took the speedometer with it. (Bam! Bam!) The speedometer appears to be rarer and more expensive than the sending unit. I paid Moma in Alberquerque $250 to repair mine and they said they may not have the parts to repair anymore these.

    Be warned. If you have a skittish speedometer, I would definitely disconnect the sending unit. There's a connector on the passenger side of the transmission that connects the sending unit to the harness. It's easily accessible by removing the rear passenger side tire.

    More on this later.
     
  8. matteo

    matteo F1 World Champ

    Aug 1, 2002
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    dennis mccains has them for $110. Make you tell them your model year, there are two different ones.
     
  9. f355spider

    f355spider F1 World Champ
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    Matt,
    You are correct, there is the one for the carb 308s', then the one for "all later 308/328's".

    Dave
     
  10. f355spider

    f355spider F1 World Champ
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    Donald,
    You make a good point, and why I try to fix stuff on my car before it gets worse or damages something else. Plus it bugs the hell out of me to have stuff not working properly!

    Dave
     
  11. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
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    Donald,

    You got your speedo worked on in ALBUQUERQUE? At "Moma?" I live in Albuquerque and have never heard of them...

    Tell me more. Do you live in ABQ?

    Or is this just a good speedo shop that happens to be in New Mexico of all places?
     
  12. Trinacria

    Trinacria Formula Junior

    Aug 7, 2002
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    Baldassare Guzzo
    The carbed ones are different but 1981 and 1980 are different as well. My (November) 81 GTBi required the 1980 unit. It was $75 at Dennis Mccann last year.
     
  13. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
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    Help me out--who/where is the Dennis Mccann source?
     
  14. Darolls

    Darolls F1 Veteran
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  15. Ferrari_co_uk

    Ferrari_co_uk Karting

    Apr 16, 2003
    245
    London, UK
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    Mark Langfield
    Hi All,

    We have the 308GTBi/QV/328/512BBi/Mondial Speedo Unit in stock and the price is £51.60 (approx $86.06)

    If anyone is interested please drop me a mail or it can be ordered securely online at www.owners.ferrari.com

    Best
    Mark
     
  16. donaldh2o

    donaldh2o Karting

    Nov 10, 2003
    143
    Irvine CA
    Full Name:
    Don
    So here's the info on MOMA:

    MOMA
    1321 Second Street NW
    Albuquerque, NM 87102
    PH: (505) 766-6661
    Fax: (505) 766-5419
    EMail: momanm@aol.com

    I don't know what their primary business is, perhaps repair of speedometers and other dash intruments. I live in Irvine, CA and dealt with them on the phone.

    Anyway, they charged me $250 to repair a 308 speedometer in which they had to replace the main circuit board and all its components.

    Maybe Mike Procopio, who lives in ABQ, could drive over there and check the place out. Just an idea.
     
  17. Birdman

    Birdman F1 Veteran

    Jun 20, 2003
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    North shore, MA
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    THE Birdman
    I have heard good things about Palo Alto Speedometer and I am sending a busted unit to them shortly. I'll report back on the cost and the repair.

    They are here: www.paspeedo.com

    Jonathan
     
  18. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
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    Not everybody has had a good experience with them, so I've read... Many people have said good things though.


    Jeff at Ferrari UK, do you have the speedo generators for the carb cars in stock?
     
  19. f355spider

    f355spider F1 World Champ
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    May 29, 2001
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    Mike,
    You are right, I have heard that one or two individuals have had bad luck with Palo Alto Speedometer, but I believe that is the exception, rather than the rule. I have sent them two clocks and one tach, and each was fixed properly, and basically delivered on time. I think the first clock I sent them, they promised to return in two weeks, and instead it took three, no big deal. All the others were delivered within the time they specified.
     

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