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Car Broke down! :/ after full revs Any help /advice?

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  • #46
    To OP,
    I 'll measure some ecu's to get the resistance values mentioned above. Obviously if yours is kaput its not much help, but it might help someone else out in the future!

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    • #47
      Originally posted by prj View Post
      If ECU is blowing fuse every time it's connected most likely the car has issues with the alternator and was overvolting the ECU.
      The ECU IIRC at 18V collapses a diode and forces ground and power together, to prevent further damage to itself.

      Measure the resistance on the ECU inputs between:
      PIN 18 and PIN 24
      PIN 27 and PIN 24

      If you read 0 ohm on any of those, then your alternator's voltage regulator is shot, causing an overvoltage and the ECU frying the diode in itself.
      The ECU then needs repair - the diode needs to be desoldered and replaced.

      If you have resistance between those pins and they are not shorted together, then at least that part of the ECU is intact.
      Ah thank you!! will note this, it has had a new alternator and it seems like a beast and aftermarket one

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      • #48
        Originally posted by prj View Post
        If ECU is blowing fuse every time it's connected most likely the car has issues with the alternator and was overvolting the ECU.
        The ECU IIRC at 18V collapses a diode and forces ground and power together, to prevent further damage to itself.

        Measure the resistance on the ECU inputs between:
        PIN 18 and PIN 24
        PIN 27 and PIN 24

        If you read 0 ohm on any of those, then your alternator's voltage regulator is shot, causing an overvoltage and the ECU frying the diode in itself.
        The ECU then needs repair - the diode needs to be desoldered and replaced.

        If you have resistance between those pins and they are not shorted together, then at least that part of the ECU is intact.
        Hey thx !! very informative! though does this information still apply if its only blowing when I turn on the ignition.. not when its just plugged in...

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        • #49
          Check the resistance on those pins, if it’s a short that is likely the issue to work on next
          Greg

          S2Forum.com Administrator & Webmaster

          '93 Coupe with a few tweeks

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          • #50
            Has anyone ever taken the fusebox out? I've undone the nuts but its held down by some gummy material and a right bitch to get off.. its not budging! anyone any tips? or have I missed something?

            thx in advance x

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            • #51
              You don’t have to remove the casing that’s glued into the car.
              The fusebox is clipped into it. Push the clips back and it will come out.

              S2 Coupe 3B Project


              Ur quattro restoration

              S2 Avant

              Boost is the new rock and roll!
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              • #52
                OMG!! im such a noob! DOH!! i was trying to prize that thing off! .. getting brain dead atm.. thank you guys!

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                • #53
                  How are you getting on with diagnosing the issues?
                  Greg

                  S2Forum.com Administrator & Webmaster

                  '93 Coupe with a few tweeks

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                  • #54
                    Originally posted by Greg_S View Post
                    How are you getting on with diagnosing the issues?
                    Just got back from the Nurburgring trip this weekend and sorting out my life. Havent got round to looking at the s2 yet, just getting my daily, the golf top mounts done, with new tyres and front aligment doing atm.. will jump back onto the s2 when I can.. Thats the update so far. will try my best at looking at this.

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                    • #55
                      Ok guys!! heres an update!! I have checked the fuse box now and opened it, still no signs of issue,

                      I managed to strip the ecu very carefully and I found something. Is this easy to fix? (its the closeup picture of the 3 connectors and one isnt looking right).

                      Who would be able to do this work? ecu specialist? an electronics guru or even me?

                      looks like a resistor of transistor im not too sure , my electrical knowledge is vague.

                      Attached Files

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                      • #56
                        That's a diode - easy enough to fix it yourself provided it's a through-PCB fixture. Just make sure you fit a new one with the bar on the right side - the bar represents the line at the end of the triangle on the diode symbol.

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                        • #57
                          Yes should be easy to replace. Looks like a 1N4001 but happy to be corrected https://uk.farnell.com/multicomp/1n4...791?st=1N4001+

                          Hopefully that solves your issue
                          Greg

                          S2Forum.com Administrator & Webmaster

                          '93 Coupe with a few tweeks

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                          • #58
                            Hey this sounds cool, and thankyou, but diodes shouldnt just blow? Is it likely that something else could have caused this?

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                            • #59
                              That's the overvoltage protection zener. Your voltage regulator is probably shot, it blows at 18V IIRC.
                              No idea why it's tilted to the side though. But maybe it got hot enough that it melted the solder.

                              If it is what I think it is then it is not a standard diode, in fact if you put a standard diode in you'll blow the ECU fuse all the time I think.

                              The ECU schematics are posted in the forum, easy to verify.
                              http://tuner.ee - http://www.facebook.com/tuner.ee

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                              • #60
                                Originally posted by prj View Post
                                That's the overvoltage protection zener. Your voltage regulator is probably shot, it blows at 18V IIRC.
                                No idea why it's tilted to the side though. But maybe it got hot enough that it melted the solder.

                                If it is what I think it is then it is not a standard diode, in fact if you put a standard diode in you'll blow the ECU fuse all the time I think.

                                The ECU schematics are posted in the forum, easy to verify.
                                Huge thank you

                                hmmm.. I may send it off to an ecu specialist.

                                can you explain what a voltage regulator is? is that in the ecu?
                                I dont have much knowledge on these things thx

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