nickolai Posted August 25, 2011 Share Posted August 25, 2011 (edited) I gotta say, the old Subies been doing pretty good for all the abuse I've given it lately. The last head gasket job seems to have sealed well, and it's been nearly five months with no overheating! Anyway, I'm hoping you all can help me solve a mysterious electrical issue that has recently cropped up: So I go out and start up the car one night (88 DL EA82 SPFI 5spd), and the headlights are noticeably dimmer, growing brighter as rpms increase. My first thought was bad alternator, but it's been a couple weeks and a couple hundred miles, and it still starts up just fine. I am sure that the battery is being charged. Starting at the same time as the dim headlight issue, the radio will mute for about 2 seconds on most downshifts, and each time the headlights are switched off. Like I said, I have been driving for some time with these issues, and they don't really seem to be getting worse, but I would like to take care of it before they do. The only place I can think of where the headlights, radio, and rpms cross paths is at the alternator, but it's at least still charging that battery so I know it's not totally dead. The only alternator test I know how to do with my multi-meter is to test the battery volts with the car running. I get 14.2v across the battery with the engine at idle. Anybody got any other alternator tests or ideas? Thanks in advance for any help! Nick Edited August 25, 2011 by nickolai Quote Link to comment Share on other sites More sharing options...
Dj7291993 Posted August 25, 2011 Share Posted August 25, 2011 See what the voltage does when you rev it. I don't have a lot of experience, but my first though is voltage regulator. As far as alt. tests, take it to the parts store, the have the equipment to do a quick test. Not a lot of details from it, but it might be a start. Quote Link to comment Share on other sites More sharing options...
idosubaru Posted August 26, 2011 Share Posted August 26, 2011 i'd clean both battery terminal connectors and make sure they are clean and not loose/degraded/corroded. then check the plug at the alternator. then check the output of the alt with every electrical draw you can think of turned on - radio, lights, door open, fogs, heat, flashers, etc. check output at alternator and at + terminal of battery - what do you get for each of those? some people even just run a heavy gauge cable straight from the alt output to the positive terminal...but double check that, been awhile since i've done an EA but pretty sure they're the same, i do have one in my driveway. jumper cable another car to it and see if the batteries get brighter. sounds like alternator but 14.2 seems like a good reading. Quote Link to comment Share on other sites More sharing options...
Txakura Posted August 26, 2011 Share Posted August 26, 2011 (edited) nvm, I had thought it was the regulator and a diode failing, but that wouldn't put out 14.2 at an idle Edited August 26, 2011 by Txakura Quote Link to comment Share on other sites More sharing options...
Cougar Posted August 26, 2011 Share Posted August 26, 2011 Like Grossgary stated, clean the battery terminals. While the alternator may be putting out a good output it will be diminished if the battery connections are dirty. This is most likely the trouble. If that doesn't help then have the battery tested to check its' capacity. Also try cleaning the battery to chassis ground. Quote Link to comment Share on other sites More sharing options...
987687 Posted August 26, 2011 Share Posted August 26, 2011 Test for ripple. Put your meter on AC and check the AC voltage in the system. Shouldn't be more than about 1v AC. If it is, you have bad diodes. That will cause all sort of problems in the electrical system. Quote Link to comment Share on other sites More sharing options...
Cougar Posted August 26, 2011 Share Posted August 26, 2011 Test for ripple. Put your meter on AC and check the AC voltage in the system. Shouldn't be more than about 1v AC. If it is, you have bad diodes. That will cause all sort of problems in the electrical system. Actually, if the AC ripple voltage is more than 0.1 volts AC there is a problem. One volt of AC is way too much for the battery to handle. Quote Link to comment Share on other sites More sharing options...
nickolai Posted September 2, 2011 Author Share Posted September 2, 2011 Well thanks for the help everyone. I never did get it figured out, and then last night I blew the head gaskets AGAIN. Oh well. At least my rebuilt EA81 is almost done so I can just say goodbye to the EA82 for good. Quote Link to comment Share on other sites More sharing options...
Loyale 2.7 Turbo Posted September 2, 2011 Share Posted September 2, 2011 The Electrical problem you Described is Related to a Bad Grounding... so I Kindly Suggest to do one of this Two things: Remove the Grounding Wires from all its Terminals, Clean Both Surfaces and reinstall. Run a New Parallel Ground Wire. I Did Both Long Time Ago... I Hope this can Help, Good Luck! Kind Regards. Quote Link to comment Share on other sites More sharing options...
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