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  1. #1
    Miker is offline Registered User
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    Default Volvo Penta 2010B Tachometer problem

    In fixing a loose connection in the instrument panel which prevented the engine from starting, my more knowledgable crew has moved onto another problem. The tachometer no longer registers the revs but swings at about once a second from one side of the dial to the other. We have checked the connections and found a steady 12 volts from the alternator lead to the tachometer on the + side whatever the engine speed. What we are wondering is where the lead from the - side goes (It is not shown on the Penta handbook wiring diagram) and what current varies to cause the tachometer to register the revs.
    Can anyone give a laymans guide to this, please?

  2. #2
    VicS is offline Registered User
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    Default Re: Volvo Penta 2010B Tachometer problem

    The positive supply is the blue/red wire. It is switched on when the key switch (or panel switch) is turned on and it also supplies the electronic module and any other instruments. The negative supply is from the black wires that connect the negative to everythng (inluding a negative for all the illumination bulbs.

    One of the other two connections that go to the umpteen way connector is the signal from the W terminal the other actually goes nowhere.

    Sorry my bband connection has gone tits up so I cannot access a manual at present to tell you which of those two goes to W

    Sorry may be not much help but the panel wiring diagram in either the owners manual or the w/shop manual does show it all.

  3. #3
    Miker is offline Registered User
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    Default Re: Volvo Penta 2010B Tachometer problem

    Thanks. We've got a workshop manual and were puzzled over the S- grey lead that went into the big connector at 12 but did not appear to emerge on the other side on the engine wiring diagram.
    If the lead from W on the alternator carries the signal to S+ on the tachometer, should it vary in voltage as the revs change and is the S- lead which apparently goes nowhere, a lead to earth? What we are puzzling over is what changes to cause the tachometer to register the correct revs.

  4. #4
    VicS is offline Registered User
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    Default Re: Volvo Penta 2010B Tachometer problem

    Equally puzzled by the grey wire on S-

    The signal from W is an unrectified output (possibly from just a tapping ) from one of the stator coils. The volts will be AC and will only rise to the point when the regulator starts to control the alternator. The Tacho measures the frequency of the signal not the volts.

  5. #5
    Miker is offline Registered User
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    Default Re: Volvo Penta 2010B Tachometer problem

    Thanks again. Went to the boat this morning and the engine was as dead as a dodo. The instrument panel would not light up nor would the engine turn over. I now suspect an intermittent fault in the power on/off switch which I will replace. I did notice a loose connection in the toggle switch lead (14 on wiring diagram) from the power on/off switch (10) R/Bl 15, and am wondering what effect that would have.

  6. #6
    VicS is offline Registered User
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    Default Re: Volvo Penta 2010B Tachometer problem

    That red/blue wire is the power supply from 10 to 14 that is required to energise the glowpug relay when 14 is closed. If it is disconnected you will not be heating the glowplug prior to operating the starter.

  7. #7
    Miker is offline Registered User
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    Default Re: Volvo Penta 2010B Tachometer problem

    That 14 connection must have been in place when we managed to start the engine then. I must have dislodged it again when poking around. We will have to ensure that it is connected tightly.
    Any ideas on what could cause the tacho to oscillate? A replacement tacho costs 164 from Keypart so I don't want to go down that road if I can avoid it, especially as we tend not to look at it anyway - just going on the engine noise.

  8. #8
    VicS is offline Registered User
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    Default Re: Volvo Penta 2010B Tachometer problem

    Cant help with the tacho apart from saying check all connections incl the W connection on the alternator. Sorry

  9. #9
    Miker is offline Registered User
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    Default Re: Volvo Penta 2010B Tachometer problem

    Thanks again for your help. I will return to the tach once the new on/off switch arrives.

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