idosubaru Posted August 31, 2011 Share Posted August 31, 2011 has anyone ever had a failed diode before in the wiring harness? i think i may but can't find much of anything about it. i'll try to find the wires going to it so i can test or rewire in another diode. it's buried in the wiring harness behind the dash/side wall area on the drivers side somewhere and i haven't been able to locate it. the details: i was tracking a battery drain. it's looking likely that it's related to the retractable headlights. over a year ago i tried getting my retractable headlights to work - they don't go down, only come up and stay up. i replaced every single component in the system - motors, relays, timer, controller, fuses, everything. no change. so i'm thinking these two are related - and on the FSM wiring diagram there is a diode for the retractable headlights (indeed the only part i haven't replaced) and Google says diodes can cause a drain. also - my alternator was causing a 75 milliamp drain at the two wire connector (not the lead). replaced that and no more drain there. so either the bad diode fried the alternator or the alternator fried the diode? i'll try and post a picture of the FSM wiring diagram and see if anyone can help me. Link to comment Share on other sites More sharing options...
eulogious Posted August 31, 2011 Share Posted August 31, 2011 Ya, a diode will stop any voltage flowing one way, so I could see it preventing a drain for sure. To test the diode, test the 2 ends of the wire using the diode setting on a decent DMM. If it's bad, then the meter should tell you. Easier said than done I realize... Another thing you could do is just run a new wire with a diode wired in and see if it solves your problem. Just bypass the old wire with a new one and a diode wired in. Shouldn't be too hard I would think. Just make sure the diode is wired in the correct way. Strange, but not unheard of to see a diode give out, but definitely strange. Sounds like you are getting closer to solving your problem! Link to comment Share on other sites More sharing options...
idosubaru Posted August 31, 2011 Author Share Posted August 31, 2011 ah electrical people, high five! i'll try again and see if i can't find each "end" for testing. question - (keeping in mind i don't know wiring lingo) - if i locate one end, there's another connection somewhere between the end and diode so says the FSM - can i still test the diode even if another wire is connected somewhere between where i'm testing and the diode? for example: XAAAAAAAABAAAACAAAAAAAY if the diode is "C" and i'm testing with the DCCM at X and Y but there's wire connected somewhere at "B" - will i still be able to test the diode or will that wire at B hose it up? this also complicates the 'run another wire/diode' scenario but it's only one or two so maybe it's not too bad. i'm not good with wiring. Link to comment Share on other sites More sharing options...
eulogious Posted August 31, 2011 Share Posted August 31, 2011 (edited) I would think that it shouldn't matter if the wire goes through several junctions, as it should still function a certain way no matter what. The diode should prevent voltage going through that wire a certain way, no matter if it goes through 50 junctions, and you should be able to test it the same way. Even if multiple wires come off of it, it is still connected to the diode at some point, so you should be able to test it with no issues from any of the wires that feed into/out of the diode. But that brings up another point… Maybe there is some corrosion in the different junctions? Might not be a bad idea to try to check that out. Another way to get around the junction issue is to find which junction the diode is at, and just test that section by completely unplugging both ends of the circuit. Again, easier said than done of course Edited August 31, 2011 by eulogious Link to comment Share on other sites More sharing options...
Cougar Posted August 31, 2011 Share Posted August 31, 2011 my alternator was causing a 75 milliamp drain at the two wire connector (not the lead). replaced that and no more drain there. so either the bad diode fried the alternator or the alternator fried the diode? There may have been a voltage spike that caused the diodes to fail. It is hard to say if the failures were related or not. You can check the diode as long as there is no other path for the test current to flow. That is why isolating one end of the connection is a good idea. Link to comment Share on other sites More sharing options...
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