Ignition control modul...help!

Discussion in 'Engine' started by Stringer, Sep 24, 2012.

  1. Stringer

    Stringer Hardcore MB Enthusiast

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    Does anyone know how to check one of these with a simple multimeter? I think mine is over-heating due to the heatsink behind it drying out - but before i roll my sleeves up and pull it off, i wondered if anyone knew the ohm readings?

    Also, is there a paste which i could buy in a hardware store which would work just as well for the thermal gel?

    thanks again
     
  2. andy27168

    andy27168 Hardcore MB Enthusiast

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    Hi,
    Can,t help with what the readings would/should be but if you get no definitive feedback what these readings should be I would be inclined to remove the unit, clean up the surfaces and reassemble with new paste.
    If you have a local Maplins, RS Components near you should be able to get some heatsink compound/paste.

    High Thermal Conductivity Heatsink Compound : PCB Compounds : Maplin Electronics
    Buy PCB Compounds and Adhesives SMT silicone heat sink compound,20ml RS ERHP20T online from RS for next day delivery.
     
  3. grober

    grober MB Club Veteran

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    Your problem is that that any fault will only occur at high temperature so testing cold would return normal readings. Usually its the power transistors that go faulty when they heat up but the quickest way to check the unit is by simple substitution. Try a different unit and the problem goes away= result. There used to be specialist companies in Germany who rebuild/tested them. there are some posts on here with contact addresses or you could try ebay.de
     
  4. OP
    OP
    Stringer

    Stringer Hardcore MB Enthusiast

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    thanks to both of you. IN FACT i got a friend who is getting some freeze spray, which she reckons is used by offices here to clean computers (is it nitrogen?).

    But Andy, can i ask you. Is there a substitute product for the conventional compound paste? I ask, as although there is a Radio Shack here, i am certain that they will only sell this in tiny tubes for computer processors. And being Lebanon, it will be 3 times what you would ever pay for it in maplins in the UK. But what about something which would work from the hardware shop?
    thanks
     
  5. Stratman

    Stratman Hardcore MB Enthusiast

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    Bite the bullet and get the proper heatsink compound.

    If manufacturers could use something cheaper they would. The fact they don't should tell you something.

    You don't buy a Mercedes to save money :D
     
  6. grober

    grober MB Club Veteran

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    Computer air dusters aerosols which what I believe your friend is referring to normally contain something like dimethyl ether and some form of inert fluorocarbon like tetra fluoroethane-- while these will have a momentary cooling effect it will not last long enough to be an effective test imho. There are different grades of electronic thermal heat sink compound- the cheap stuff will be fine don't bother with expensive silver computer CPU stuff. To be honest if the unit has gone faulty then it means the transistors are probably damaged already but only showing it when hot. You MAY be able to retrieve/aleviate the situation by application of new heat sink compound but the damage may already be done.
    Its all a cost v. benefit thing. The freezer spray and heatsink compound will help pinpoint the fault if its one of those components that's overheating BUT will be unlikely to cure it in the longer term.
     
  7. OP
    OP
    Stringer

    Stringer Hardcore MB Enthusiast

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    i have looked all over for heat sink compound but with no luck, although i take your points about 'biting the bullet' which means something completely different out here in Lebanon.
    For the moment i put some black silicon sealant between it and the car body and i THINK this has done the trick as it wasn't misfiring when i drove it for 30 mins in traffic today at full operating temp. but it's all about isolating the problem, isn't it? Once you're found it for sure, then you can move on and not waste money just throwing parts at it, which i think i have achieved today, thanks, i must say to you all.

    ps. can't you repair them though if they only have blown resistors inside?
     
  8. grober

    grober MB Club Veteran

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    The problem on the repair front is that the components found inside these units are unbranded/ unmarked --- this makes straight replacement of a faulty ignition power transistor difficult. Many of the components are encapsulated to prevent damage by vibration or damp and sometimes the power transistors are glued to their respective heatsinks rather than bolted. Some repair specialists have "back engineered" these power transistors by dissection and test of damaged units but they keep that info a trade secret. If the chip that stores the reference ignition advance map has gone the device is regarded as irreparable even by the experts.

    What you have done will not have helped the overheating as the function of the heatsink compound is to help heat transfer from the unit to the metal of the inner wing,----unless the silicon sealant is doing this in some way?????? However you may have helped remake some electrical connections somewhere. Lets hope the problem is solved.
     
  9. OP
    OP
    Stringer

    Stringer Hardcore MB Enthusiast

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    are you saying that a thin film of silicon evenly spread would not help at all with the heat transfer from the unit to the car's body? Before, there was nothing underneath it at all and it was not even bolted on properly. When i put it on, i did ask myself how any latent heat transfer could happen with silican and i guessed that a very thin film would probably take some heat out of it. Don't forget it's a hot country here.
     
  10. grober

    grober MB Club Veteran

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    Without knowing the composition of the silicon sealant difficult to say as there are silicon based heat transfer compounds. Having the unit firmly bolted to the wing will certainly help---- if it works then not a problem.:thumb:
     
  11. panason1c

    panason1c Hardcore MB Enthusiast

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