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Instrument cluster gauge illumination issue 900

posted by  Keswick7 on  Fri Nov 10 22:41 CST 2023
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Wondering if anyone here might have further insight regarding what was described on a electrical diagram for the cluster as simply " solid state '. It is a square module under a metal cover on the left side, mounted with four small phillips screws and it apparently is part of the circuit that supplies voltage to the main bulbs for the speedo, tach, climate control, shift console etc.

I do get voltage at one screw where the trace leads to the bulbs but notice there is also voltage present on both sides of where the bulb holder makes contact. I gather one side should be ground.The bulbs all function but nothing at this point when secured to the circuit board.


There is a small IC on the board for the module, the cluster is a Yakuzi and I understand the earlier VDO clusters had something similar but with a fusible link.


Also have intermittent issues with the speedometer but have a feeling it is related to either the connector or wires at the speed sensor. Vehicle is a 1994 945T








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    Instrument cluster gauge illumination issue 900

    posted by  B.B. on  Sat Nov 11 20:14 CST 2023
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    last visit: Mon Oct 6 13:15 CST 2014
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    Hi ___?___,

    Don't be confident with re-flowing "all of the joints".
    The flex board has two sides and creepy through hole connections for circuit tracks.

    I had no luck re-flowing the bad through hole connection for the circuit track
    to the fuel gauge
    Tacking a short jumper did the trick.

    I sent you schematics from the Volvo book.
    Post back with your results.

    Bill








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    Instrument cluster gauge illumination issue 900

    posted by  Keswick7 on  Sat Nov 11 15:37 CST 2023
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    Hello Bill - I have been checking on availability of a Volvo green booker this 940, absolutely necessary as you suggested. I did reflow all of the connections but will definitely have to take the cluster out and look closer at the multi pin connectors. I have yet to check the speedo sensor so need to address that in case it is the issue.


    I appreciate any help - I believe the schematic I was checking is not from Volvo, a bit basic but at gave me some information. My email is urago1952@gmail.com







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    Instrument cluster gauge illumination issue 900

    posted by  B.B. on  Sat Nov 11 04:11 CST 2023
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    last visit: Mon Oct 6 13:15 CST 2014
    [RELATED]

    Hi,

    Define carefully everything that has failed on your instrument cluster.
    What lights fail to work , and what happens to your speedo?
    What schematic are you working with?
    What you want is the Volvo wiring diagram TP3904202
    Find a PDF file on line if you're lucky with uncooperative search engines,
    and check at Ebay and used book dealers such as Abe book.

    That metal box sounds like the Rheostat.
    Confirm that the dimmer switch for the lamps is behaving or not.

    Failures of the instrument cluster are often bad solder joints that require
    careful reflow and/or jumpers to resolve intermittent through hole connections
    where the circuit track goes from one side of the flex card to the other.
    Take care that you don't melt the flex card.

    Another failure can be loose connector pins.

    When troubleshooting an intermittent fuel gauge I finally caught the +12v to the gauge quitting and then probed back to a ratty through hole connection.
    A jumper solved that, and there was also a loose pin for for the tank sensor.


    For your speedo, start with the 4 pin connector "D" in the center of the board.
    1 Signal +
    2 Signal -
    3 -
    4 + 12v from ignition switch

    The speedo is grounded via Connector A pin 2
    You'll see this in the Volvo wiring info

    Yes there is an in-line fuse 11/41 to the speedo D-4
    This fuse is common for all of the gauges

    Check the series component from D2 to Speedo S -
    it is likely a capacitor.

    What's your email ? I'll send you Volvo instrument cluster schematics.

    Bill






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