Vito W638 clocks...malfunctioning, of course.

Discussion in 'Electronics' started by BK127, Mar 24, 2012.

  1. BK127

    BK127 New Member

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    Joined:
    Sep 19, 2011
    Car:
    Mercedes-Benz Vito 108cdi
    I have a 2001 W638 Vito, ex-Traveliner, now a dayvan conversion. The interior-fittings-part of the conversion was a DIY job (although to a superb standard - the previous owner fitted out canal boats), but the auxiliary electrical system (leisure battery, split-charging system, etc) was installed by a professional auto electrician. I mention that in case it should have any bearing on the electrical gremlins outlined below.

    For as long as I have owned this van, the instrument panel has had issues. I know that this is a very common problem on this generation of Vitos, so rather than buying a scrap part (probably just as faulty) from eBay, I sent it to ACtronics in Colchester for a complete rebuild. When it came back, I refitted it to the van...and there was no difference. I rang ACtronics, they said return it, they checked it, and it came back with a clean bill of health. Still no change.

    Here are its particular idiosyncrasies:

    The needle gauges will frequently die while I am driving: the speedo and tacho freeze where they are, and the fuel and temp gauges fall to below zero. Generally, they'll stay there, and won't come back to life until the engine is stopped, left for a while, and then restarted. Of course, now they are sitting at 60mph and 2,500rpm or whatever, so will give utterly ridiculous readings. They will reset if the ignition is turned off and on several times: turn the ignition on, wait for the warning lights to illuminate, turn it off again, and the needles will drop roughly 20mph and 1,500 rpm respectively. Do this until they are at zero, and you are good to go. Until, of course, the whole thing expires again five minutes later. While the needle gauges are in this state of death, everything else - all warning lights and most of the illumination (more on that later) still function as normal.

    So far, so typically Vito. But there are a couple of strange things that I have noticed:

    After I park up (invariably with dead gauges) and turn the engine off, no amount of coaxing (via the turning-the-ignition-on-and-off trick) will tempt the clocks back to life, until I open the driver's door. I assume that the contact switch for the interior light makes its connection, and somehow (bad earth?) this energises the instrument panel. I'm not imagining it; as I open the door, the fuel and temp gauges come back to life, jumping back up to zero. It doesn't matter whether the interior light is switched to "off", and therefore not part of this operation: the effect is the same. Also, you can switch the interior light on and off as much as you like without opening the door, with no effect. The door has to be opened.

    And the other thing: the illumination for the fuel and temp gauges has never worked, not when I first bought the van, not after ACtronics' first rebuild, and not after their subsequent check, in which they specifically addressed this issue, amongst others.

    One thing I should mention: it is possible to isolate the auxiliary electrical system in the van (the one installed for the dayvan conversion), and this makes no difference to the issues outlined above. So the culprit lies elsewhere, I should imagine.

    Clearly, there's some problem with the supply to the instrument panel, then. Is there anyone out there with any ideas or suggestions, or a similar experience? Well, there are probably thousands upon thousands of W638 owners with similar experiences, but has anyone managed to find a cure or solution? One that doesn't involve four gallons of petrol and a match, that is.

    Thanks in advance for any help, suggestions, sympathy, commiseration, practical advice, feedback, jokes, abuse, whatever.
     
  2. SPX

    SPX MB Club Veteran

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    Ap Norf
    Car:
    That one
    One of the joys of 638 ownership is that you could spend a lifetime trying to sort out the myriad of electrics and still get nowhere.

    I would get a second opinion in the work you've had done to the dash/speedo though, something seems amiss.

    I'll start the abuse and jokes a bit later on...
     
  3. OP
    OP
    BK127

    BK127 New Member

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    16
    Joined:
    Sep 19, 2011
    Car:
    Mercedes-Benz Vito 108cdi
    Hi there, SPX.

    Yes...a second opinion would be a good idea. Shame that the only place I could take the bloody thing to around here is about 50 miles away They attempted to diagnose the issue with the clocks some time ago (before I had them rebuilt) via the diagnostic socket under the passenger seat, but could find nothing. More precisely, they couldn't communicate with the instrument panel from the diagnostic socket, which suggests either a faulty panel, or some separation in the spaghetti of wiring between it and the socket.

    Perhaps I need a wiring schematic for the instrument panel multi-plugs. Strange how some of the panel is always functional (e.g. all warning lights), but the needle gauges are intermittent. And utterly baffling why the fuel and temp gauge illumination sullenly refuses to work.

    The chap I spoke to at ACtronics the second time around said that they had "replaced some bulbs" in the panel (conveniently not covered by their 2-year repair warranty). Indeed, the digital display now illuminates, where it didn't before. But, unless the fuel and temp illumination bulbs are blowing as soon as the panel is connected...

    Ah, I have no idea. I'd live with it, but it's never going to pass an MOT like this.It' s already cost me in the region of £240 to get this far with the bloody thing, and really the only tangible change is that the digital display now illuminates. It won't display the time for more than twenty seconds before returning to the outside temperature, but I can live with that...
     
  4. Danny DeVito

    Danny DeVito Hardcore MB Enthusiast

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    Possibly the wires in the door are shorting where the wiring loom comes through into the door. Remove the panel and pull the loom into the door a bit and check it, theres lots of spare cable to pull it in. I pulled mine and cable tied it so that fresh cable is now at the bendy bits. I found wires frayed and wires broken causing things like intermittant central locking and odd interior lighting. I think all gauges should be lit from the same source like a few bulbs. I'll have to think about the other stuff
     
  5. Danny DeVito

    Danny DeVito Hardcore MB Enthusiast

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    Or maybe just unplug the whole door wiring inside under the dash. You can see where they go out through the hole. Find the plugs and take them apart then see if it makes any difference. Get a spare cable tie for refitting the plugs up.
     
  6. OP
    OP
    BK127

    BK127 New Member

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    16
    Joined:
    Sep 19, 2011
    Car:
    Mercedes-Benz Vito 108cdi
    Thanks, DdV. I'll try your suggestions. The wiring in the door boot may well be an issue, as my central locking has the dreaded lock-unlock-lock sickness. If that's the case, it'll be a relatively easy fix. If it's a red herring, and the problem lies elsewhere...then it could be a nightmare.

    As you say, all illumination should be powered from the same source. Bizarre too how all the warning lights work perfectly, all of the time, yet the needle gauges are intermittent. That's why I originally thought that the fault was in the panel itself. After the rebuild, this cannot be the case.

    I see you're in Ireland...whereabouts? I'm on the Dingle peninsula, Co. Kerry.
     
  7. Danny DeVito

    Danny DeVito Hardcore MB Enthusiast

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    886
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    Ireland
    Car:
    V220 CDI
    The central locking switches are in the locks. The switches in the door frame only operate the interior lights. My boot lock switch had a lever which wasn't pressing properly. thats why mine was locking unlocking. Now sometimes the slide door doesn't connect properly.

    The dash has a few bulbs for lighting. Then the light is spread about by clear plastic bits. Maybe the bits that should go to the fuel gauge is gone ?

    Your gauges may still be faulty of course. I would think its difficult to see a full and normal operation on a test bench. Best option would be to test in another car or get another speedo. It would fit in some vitos i think. Thats difficult to do of course.

    When you open the door it may be a result of power shorting from the lock rather than the door switch. I will try find the wires which supply negative to the clocks etc. I don't think it odd that the warning lights stay on, as we have no idea with all those wires there about what powers what.
     
  8. Danny DeVito

    Danny DeVito Hardcore MB Enthusiast

    Messages:
    886
    Joined:
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    Location:
    Ireland
    Car:
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    Pin 2 supplies ground signal into the cluster, not sure which plug though. Brown and white wire it is. It feeds into the control part of the cluster which also powers the speedo etc. After thats it anybodys guess.

    I'm in Kildare
     

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