Tach stopped working in a heavy down pour of rain? | FerrariChat

Tach stopped working in a heavy down pour of rain?

Discussion in 'Mondial' started by buck74, Jun 17, 2018.

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  1. buck74

    buck74 Rookie

    Dec 14, 2016
    30
    Eau Claire, WI
    Full Name:
    Frank Buckles
    I do not like to drive my 3.2 convertible in the rain but got caught out in a sudden heavy downpour / thunderstorm. With the mid level engine being quite exposed I hoped for the best, then my Tach stopped working? Not sure if this is a related to the rain water or not. I have not driven it since. Any advice? Thank you. Buck
     
  2. Plutexams

    Plutexams Rookie

    Mar 31, 2018
    21
    Full Name:
    RICHARD R PLUT
    The tachometer sensor operates off the flywheel and I believe it is on the left side of the engine (towards the front of the car). I'd start by checking the plug where the sensor plugs in. It might be corroded. Plugging and unplugging the sensor a couple times may be enough.
     
  3. djs308

    djs308 Formula 3
    Silver Subscribed

    Sep 2, 2002
    1,100
    Long Island, NY
    Full Name:
    David S.
    A while back, my tach became intermittently functional. Had it checked out. Source of the issue was traced to the infamous fusebox up front. That might be the best place to start troubleshooting. Good luck!
     
  4. MvT

    MvT F1 Rookie

    May 25, 2013
    4,248
    The Netherlands - NH
    Full Name:
    Tijn
    The sensors are waterproof :) but my guess it is your fuse board seeing David's comment. Although it is in a closed area you might think it is protected by rain, but it isn't due the single lock mechanism of the bonnet. When driving at higher speeds it wobbles (Just look at the edges near the window while driving) and rain pours in.

    I guess take it out and let it dry and perhaps it starts working again.
     
  5. buck74

    buck74 Rookie

    Dec 14, 2016
    30
    Eau Claire, WI
    Full Name:
    Frank Buckles
    Thanks everyone. I was actually surprised how little rain (that I could see) came through the soft top. I will give your ideas a try. Buck
     
  6. MauroV

    MauroV Karting

    Jun 24, 2013
    152
    Italy
    Full Name:
    Mauro
    When mine doesn't work I just tap on the glass to get it going again. Worth a try.
    Mauro
     
  7. afterburner

    afterburner F1 Rookie
    Silver Subscribed

    Jun 20, 2008
    3,197
    Hong Kong
    Frank, the tach signal is given via the pin 10 (brown-black wire) of the ECU cylinder 5-8 (left or front bank).
    If the tach lights work, the ground is ok. It's shared by the illumination and the instrument.
    The remaining wire is a 12V positive to the instrument.
    The fusebox isn't involved here.
     
  8. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,036
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #8 Steve Magnusson, Jun 26, 2018
    Last edited: Jun 26, 2018
    A 3.2L uses the single ECU MicroPlex, not the dual ECU DigiPlex (but all of afterburner's points are still valid). The tach signal is generated by the MicroPlex ECU so, if the engine runs, that's a very strong sign IMO that the flywheel sensors are OK, and the trouble is something in the tach itself or its wiring (or, heaven-forbid, the MicroPlex ECU) - I like MauroV's suggestion to give it a tap, or few taps, while the coachwork is in motion to see if anything happens (I can't recall if both the 3.2 speedometer and 3.2 tach have a calibration potentiometer with a sliding contact, but that's where I'd start the search for prior threads -- just a thought...). The next diagnostic level would be to make an AC voltage measurement (or Hz measurement) between the tach signal from the MicroPlex ECU pin to ground when the coachwork is in motion (so just unplugging/replugging the MicroPlex ECU is another easy preliminary thing to try, but no one gets that lucky ;))
     

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