Mondial QV Rev Counter Troubleshooting | FerrariChat

Mondial QV Rev Counter Troubleshooting

Discussion in 'Mondial' started by MaseratiMike, Nov 4, 2017.

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  1. MaseratiMike

    MaseratiMike Formula Junior

    Mar 15, 2016
    350
    UK
    Full Name:
    Mike
    Hi Folks. Now I have my QV Coupe back I want to sort the little jobs out.

    Can someone please tell me where to locate the sensor and even a wiring diagram for the rev counter. Also anything to help troubleshoot why my rev counter doesn't work? (Loose wire or connection maybe?)

    Thanks in advance
    Mike
     
  2. Pero

    Pero Formula Junior
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    Apr 22, 2011
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    Sweden
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    Peter R
    If the engine starts I do not beleive it is the sensor. Not sure here, but I think that if the sensor is out, the engine will not start. Need help here, can someone else help please. The sensor is relatively easy to change, will look for picture.
    Peter
     
  3. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,829
    Isle of man- uk
    Send me an e mail address and will scan the wiring dia. The rev counter on mone used to cut in and out on rough roads
     
  4. MaseratiMike

    MaseratiMike Formula Junior

    Mar 15, 2016
    350
    UK
    Full Name:
    Mike
    Thank you Mike. My address is: [email protected]
     
  5. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,829
    Isle of man- uk
    E mail with wiring diagrams sent- anyone else want a copy while i am at it ?
     
  6. MaseratiMike

    MaseratiMike Formula Junior

    Mar 15, 2016
    350
    UK
    Full Name:
    Mike
  7. afterburner

    afterburner F1 Rookie
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    Jun 20, 2008
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    Most welcome. If your engine runs normally, it's not the sensor.
     
  8. stekkefun4

    stekkefun4 Formula 3
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    Nov 22, 2006
    2,232
    Belgium - Europe
    I have the same issue at the moment with mine.
     
  9. afterburner

    afterburner F1 Rookie
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    Jun 20, 2008
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    Hong Kong
    There is a pot on the rev counter that might corrode. Mark its position, spray contact cleaner, move it left and right and reposition it on the mark. It might restart your instrument. Same trick might fix a lazy speedo too.

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  10. MaseratiMike

    MaseratiMike Formula Junior

    Mar 15, 2016
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    UK
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    Mike
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    I spent a little bit of time this evening trying to diagnose the issue further, without looking at the sensor or engine management side.

    1) Removed the rev counter out of the dash (4x screws) and started the car (starts no real problem)
    2) I held a digital multimeter on DC Voltage reading - negative probe on the black middle ground terminal wire and positive probe on the green/black terminal wire on the back of the rev counter. Reading was a constant ~12.8Volts. <Confirms no wiring of supply issue there>
    3) Then I held the positive multimeter probe on the brown/black terminal wire, with the negative probe on the black middle terminal wire. At engine idle was measuring ~0.5V and revving the engine increases the voltage reading. I suspect this is normal as would indicate higher revs = higher voltage readings, to make the sensitive counter spring in the dial move?
    4) I decided to then dismantle the casing and took off the holding glue on the potentiometer in place, marked the position and rotated it backwards/forwards a few times. Then plugged the rev counter terminals back in and restarted the engine <Unfortunately still no movement of the rev counter>

    So it appears the rev counter itself has malfunctioned. Next step is to potentially desolder and replace the SAK215 IC circuit, as that is the 'brains' of the rev counter electronics beyond the capacitors/resistors. The rest of the mechanical weight and spring mechanism look in nice condition, nothing dislodged or burnt out.

    All else fails I will have to buy a replacement unit. Stefan or anyone else - not sure if you are having the same voltage readings on the wiring terminals, when you start/rev your car?
     
  11. stekkefun4

    stekkefun4 Formula 3
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    Nov 22, 2006
    2,232
    Belgium - Europe
    I planned on replacing mine with one of the spares I have in a couple of days. Right now, I'm doing the interior for some more days
     
  12. MaseratiMike

    MaseratiMike Formula Junior

    Mar 15, 2016
    350
    UK
    Full Name:
    Mike
    Ok sure. I have ordered a replacement SAK215 IC chip, will wait for that to arrive and solder the replacement in and see if that resolves the issue...
     
  13. MaseratiMike

    MaseratiMike Formula Junior

    Mar 15, 2016
    350
    UK
    Full Name:
    Mike
    Success! The replacement IC chip arrived today and after fitting, my rev counter now works!

    Less than £4 for the replacement IC chip.

    I will post a DIY thread of the procedure, as I took lots of photos.

    Thanks for the help guys
     
    theunissenguido, StuR and Jeka like this.
  14. afterburner

    afterburner F1 Rookie
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  15. Alden

    Alden F1 Rookie
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  16. stekkefun4

    stekkefun4 Formula 3
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    Nov 22, 2006
    2,232
    Belgium - Europe
    I replaced my rev counter with a spare one I had and now it's working.

    On the other hand, my speedometer is not working. Opened it up today but didn't see any pot meters. I cleaned it with some elec comp spray and hope it works now. Here are some pics of the intestines ...

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