al_roethlisberger Posted May 4, 2005 Share Posted May 4, 2005 So, since this has been a quandry a couple of times.... I just wanted to confirm, that while we were diagnosing the electrical problem with my 2002 LeMans, we found that there was indeed a diode installed inline between the ECU relay, and the ECU itself. So, for those considering installing the old "diode mod" to protect your ECU from overvoltage, it *seems* that at least 2002+ models do have the diode installed from the factory. If you don't know what I am talking about, see: http://paaat.guzz.free.fr/diode_transil/english.html The point is that in some instances, such as "bump starting", odd short-circuits, or other scenarios where high current could be sent to the ECU and "frying it", the installation of the diode offers some protection. The issue only seemed to present itself on older EFI Guzzis that had the older ECUs than the new M15. And a few of the older bikes have had their ECUs burnt in these scenarios. But the concern has also been mentioned here, and no one knew for sure if the new bikes were protected from the factory. So, if you want to check, just undo your relay block, and check under the ECU relay. You should be able to just "feel" the little diode through the heat-shrink. I don't know if 00-01 models have this protection, but I bet they do as well. Again, now knowing where it is, it should be easy to check. al Link to comment Share on other sites More sharing options...
jrt Posted May 4, 2005 Share Posted May 4, 2005 And if it has fried, you may not be passing current through it (referencing your thread on the ECU). That's a pretty simple hypothesis that he EE fellow will think off right off. Thanks for the info...even though I have an '01. Now I gotta go feel up my wiring harness. I feel dirty. Link to comment Share on other sites More sharing options...
al_roethlisberger Posted May 4, 2005 Author Share Posted May 4, 2005 And if it has fried, you may not be passing current through it (referencing your thread on the ECU). That's a pretty simple hypothesis that he EE fellow will think off right off. Thanks for the info...even though I have an '01. Now I gotta go feel up my wiring harness. I feel dirty. 50541[/snapback] Yeah, we thought of that, and it supposedly tested fine... but who knows. I'm sure that fella will check that, and yes... you should feel dirty Link to comment Share on other sites More sharing options...
Alex-Corsa Posted May 5, 2005 Share Posted May 5, 2005 So, for those considering installing the old "diode mod" to protect your ECU from overvoltage, it *seems* that at least 2002+ models do have the diode installed from the factory.If you don't know what I am talking about, see: http://paaat.guzz.free.fr/diode_transil/english.html al Interesting info and I was wondering about it.Perhaps I would try it on mine, with electrics I'm fairly good. Link to comment Share on other sites More sharing options...
callison Posted May 5, 2005 Share Posted May 5, 2005 So, since this has been a quandry a couple of times....I just wanted to confirm, that while we were diagnosing the electrical problem with my 2002 LeMans, we found that there was indeed a diode installed inline between the ECU relay, and the ECU itself. So, for those considering installing the old "diode mod" to protect your ECU from overvoltage, it *seems* that at least 2002+ models do have the diode installed from the factory. If you don't know what I am talking about, see: http://paaat.guzz.free.fr/diode_transil/english.html The point is that in some instances, such as "bump starting", odd short-circuits, or other scenarios where high current could be sent to the ECU and "frying it", the installation of the diode offers some protection. The issue only seemed to present itself on older EFI Guzzis that had the older ECUs than the new M15. And a few of the older bikes have had their ECUs burnt in these scenarios. But the concern has also been mentioned here, and no one knew for sure if the new bikes were protected from the factory. So, if you want to check, just undo your relay block, and check under the ECU relay. You should be able to just "feel" the little diode through the heat-shrink. I don't know if 00-01 models have this protection, but I bet they do as well. Again, now knowing where it is, it should be easy to check. al 50519[/snapback] That's a 1N4007 diode, probably intended as a "steering" diode. Since it's on the ground side of the ECU relay coil, it won't be doing diddly squat to protect the ECU. But, referring to V11 Sport schematic and looking at the ECU relay coil on the +12V side, you will note that there is a connector in series with the ignition switch wire that energizes the ECU relay. Assuming that one would want to be able to test the ECU/EFI on a bike on the production line without using the key, then you would disconnect at the connector (#57) and energize the ECU relay directly using +12 volts or some piece of test equipment. I'm guessing the diode has something to do with that function as the injection relay, which is also hooked into the ECU wiring mess, has no diode, so it is safe to assume that the diode is not performing an anti-emf function in conjunction with the relay energizing or de-energizing or both relays would likely sport a diode. Link to comment Share on other sites More sharing options...
big J Posted May 5, 2005 Share Posted May 5, 2005 Errrm yep, thats what I thought,errrm...... Link to comment Share on other sites More sharing options...
al_roethlisberger Posted May 5, 2005 Author Share Posted May 5, 2005 ...ah well, I thought I found something that was "good news" al Link to comment Share on other sites More sharing options...
Alex-Corsa Posted May 5, 2005 Share Posted May 5, 2005 That's a 1N4007 diode, probably intended as a "steering" diode. Since it's on the ground side of the ECU relay coil, it won't be doing diddly squat to protect the ECU. But, referring to V11 Sport schematic and looking at the ECU relay coil on the +12V side, you will note that there is a connector in series with the ignition switch wire that energizes the ECU relay. Assuming that one would want to be able to test the ECU/EFI on a bike on the production line without using the key, then you would disconnect at the connector (#57) and energize the ECU relay directly using +12 volts or some piece of test equipment. I'm guessing the diode has something to do with that function as the injection relay, which is also hooked into the ECU wiring mess, has no diode, so it is safe to assume that the diode is not performing an anti-emf function in conjunction with the relay energizing or de-energizing or both relays would likely sport a diode. In plain English??? . Is it working protection or not?.. Link to comment Share on other sites More sharing options...
Paul Minnaert Posted May 5, 2005 Share Posted May 5, 2005 Is it working protection or not?.. The diode there is not the transil diode as Al hoped for. Nor is it helping to protect against oever voltage Link to comment Share on other sites More sharing options...
Alex-Corsa Posted May 5, 2005 Share Posted May 5, 2005 The diode there is not the transil diode as Al hoped for. Nor is it helping to protect against oever voltage AFAIK why not using the right fuse instead of a diode.? Link to comment Share on other sites More sharing options...
luhbo Posted May 5, 2005 Share Posted May 5, 2005 AFAIK why not using the right fuse instead of a diode.? 50687[/snapback] Because fuses are slow? Because they burn under high currents but not necessarily under high voltages? I have heard that in most consumer electronic devices the inbuilt fuses are not meant to protect the circuit, they are just there to interrupt the current so the device won't catch fire. Hubert Link to comment Share on other sites More sharing options...
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