ofairlane Posted March 11, 2006 Share Posted March 11, 2006 I had posted this problem earlier in the week, my 99 Legacy would not charge, replaced alternater, replaced battery, replaced alternater again, still not charging. The alternaters were rebuilds after my mechanic removed the original, the battery is new. All connections are good, battery, ground, starter, fusible link, etc. The fuses are all good also, there is excellent continuity at the alternater to block, belts are tight and still not getting voltage all the time. It will however work occasionally which mystifies us more. To add mystery, the dash warning light does not light up, the bulb is fine but when the key is turned to on position it should light up but doesn't. Has anyone had this SAME experience happen to their car? Does anyone know the series of events that the charging system follows? I am afraid it may be in the wiring harness or the ignition switch. I doubt I have three bad alternaters and I know someone knows the answer to this problem, so chime in when you can. Also, if the charging system(wiring to the alternater or from) needs to be grounded, does anyone know a good bypass do do? Let me have it! DanO:confused: Link to comment Share on other sites More sharing options...
danz75 Posted March 11, 2006 Share Posted March 11, 2006 How about the +ve wire from alternator to the battery? Make sure that all connecting surfaces are free from rust and clean. coat the mating surfaces with dielectric grease. That would narrow it down to either the alternator, battery or wire harness. If the harnesse prove to be good, then make sure that it is clamped tight. I've had one before that I thought was tight but was not when I moved the wire a little. Also check the wire to battery terminal clamps to make sure that the surface is not rusted. They only cost a few dollars so replacing them is worth it. I think i replied to your other post about this problem. When I replaced the alternator with a remanufacturered one from autozone, i had to replace them 3 times before i had a good one. I wanted to save that extra $$$ so I decided to go for the one at autozone instead of a subaru one. My mistake. I don't know if the steps will work for you but that's what I did to solve mine. let me know what you find out. DS I had posted this problem earlier in the week, my 99 Legacy would not charge, replaced alternater, replaced battery, replaced alternater again, still not charging.The alternaters were rebuilds after my mechanic removed the original, the battery is new. All connections are good, battery, ground, starter, fusible link, etc. The fuses are all good also, there is excellent continuity at the alternater to block, belts are tight and still not getting voltage all the time. It will however work occasionally which mystifies us more. To add mystery, the dash warning light does not light up, the bulb is fine but when the key is turned to on position it should light up but doesn't. Has anyone had this SAME experience happen to their car? Does anyone know the series of events that the charging system follows? I am afraid it may be in the wiring harness or the ignition switch. I doubt I have three bad alternaters and I know someone knows the answer to this problem, so chime in when you can. Also, if the charging system(wiring to the alternater or from) needs to be grounded, does anyone know a good bypass do do? Let me have it! DanO:confused: Link to comment Share on other sites More sharing options...
ofairlane Posted March 15, 2006 Author Share Posted March 15, 2006 Problem has been fixed in a roundabout way. As I was informed from others, I wired a wire from an ignition switched fuse directly to the alternator, bypassing the charge indicator circuit where my problem is. The system is now charging as it should, this is just a temporary fix till I can locate the real problem, good fix though. Thanks to those who passed this fix on to me. DanO Link to comment Share on other sites More sharing options...
seattlelegacy Posted March 15, 2006 Share Posted March 15, 2006 Wait, if you bypassed the charge indicator circuit, isn't the system constantly charging? Too much charging will kill your alternator and your battery if that's the case. Link to comment Share on other sites More sharing options...
ferret Posted March 15, 2006 Share Posted March 15, 2006 You bypass is exactly why the light is initially used. It 'excites' the voltage regulator. That's why without a bulb, a 2 wire alternator doesn't put out voltage. Now is the bulb in your dashboard the correct type? If it is too small amperage, it comes on, but will not start the regulator charging (Excite it). Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted March 16, 2006 Share Posted March 16, 2006 Can someone point to a schematic or explanation of this circuit? It seems weird to me that a simple bulb in the dash would be so critical. Carl (displaying his ignorance onec again!) Link to comment Share on other sites More sharing options...
Tiny Clark Posted March 16, 2006 Share Posted March 16, 2006 I have a simple one, but don't know how to post it. I don't think his alternator will overcharge, because it has a built in regulator. The excitation for the alternator to put anything out goes thru the bulb. If the light is good, sounds like maybe that contact in your key switch is bad. Link to comment Share on other sites More sharing options...
cookie Posted March 16, 2006 Share Posted March 16, 2006 A lot of alternators need a power line to charge. I imagine it just goes though the light circuit to provide a warning light. Link to comment Share on other sites More sharing options...
ferret Posted March 16, 2006 Share Posted March 16, 2006 When you first start turning a 2 wire regulator, it's output is nothing. You MUST provide a small amount of voltage to the exciter circuit. That comes from 12v thru the Light in the dash. Once 'excited' or charging, that circuit goes to 12v. So the dash light has 12v on each side and is not illuminated. However when the regulator fails, that side continues to draw current and keeps the bulb illuminated to indicate a charging failure. Only once have I seen a regulator short and the bulb was out and the regulator was toast. Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted March 16, 2006 Share Posted March 16, 2006 When you first start turning a 2 wire regulator, it's output is nothing. You MUST provide a small amount of voltage to the exciter circuit. That comes from 12v thru the Light in the dash. Once 'excited' or charging, that circuit goes to 12v. So the dash light has 12v on each side and is not illuminated.However when the regulator fails, that side continues to draw current and keeps the bulb illuminated to indicate a charging failure. Only once have I seen a regulator short and the bulb was out and the regulator was toast. That does seem like a simple way to work the circuit - but a very 50s type of technology! Seems like we could do better nowadays. Even using an LED would increase the reliability vastly! Another good reason to pay attention to what bulbs are working when you rotate the key through to start your car! thanx guys Link to comment Share on other sites More sharing options...
Wayne Boncyk Posted March 16, 2006 Share Posted March 16, 2006 Carl, A LED might be a bad idea, because it would need to be in series with some resistance in order to keep the current in the LED down to where it wouldn't get cooked when it was on. That might not then allow enough current to "bootstrap" the alternator. A better idea might be to have a resistor in parallel with the lamp. The current would be divided between lamp and resistor, but a value could be chosen that would allow enough current to pass thru the resistor to bootstrap the alternator regardless of whether the lamp was in the circuit or not, and still have enough to light the lamp when the alternator wasn't operating. Why doesn't Subaru do it that way? Who knows?? -- spending an additional $0.03 in parts and probably a few bucks in engineering to have it changed in order to increase reliability may not have occurred to them! Link to comment Share on other sites More sharing options...
Tiny Clark Posted March 16, 2006 Share Posted March 16, 2006 IMO, there is a better way, it's called a voltmeter on the dash. You could always use a zenor to light an LED if the voltage got below 12 volts, just to get your attention. Plain and simple... costs too much. Link to comment Share on other sites More sharing options...
ofairlane Posted March 16, 2006 Author Share Posted March 16, 2006 Ferret and Cookie, you guys are right on here. The charging system does operate as you stated, the circuit does go through the indicator lamp, it is getting 12 volts on each side, and the regulator or diodes need to get exited in order for the alternator to perform. I have learned this from other members and believe it or not, I think we taught the mechanic who did the work something new also. The system is working fine and I plan on installing a voltmeter or ammeter in the springtime to make me feel better. I do have a printout of the wiring diagram and I will post it soon. Thanks for all the help. DanO Link to comment Share on other sites More sharing options...
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