heartless Posted March 25, 2012 Share Posted March 25, 2012 (edited) 1990 Legacy LS wagon, 223K on the clock, 4EAT, AWD - has had some idle issues when warm for several months now. Friday night (sat morning actually), coming home from an event that was about an hour away, the dash warning lights suddenly lit up - thankfully i was only 1/4 mile from home when this happened. Parked it & went to bed. Had been using the headlights, stereo, wipers and defrost on low...cool, misty rain conditions. Saturday - popped the hood to check the belt for the alt. looked good, tension good. DVM showed 12.6 volts on the battery with car off. Started the car - no warning lights, idle was fine. DVM showed 14.01 volts just after starting, and 14.07 after it had warmed up a little (about 5 minutes or so). I had picked up an aftermarket voltmeter a while back, decided to finally get it installed to keep an eye on things... drove into town to make use of the shop at the other half's workplace. several hours later (operating on 5 hrs of sleep) voltmeter is installed and operating properly - showing just a baby fine hair shy of 14 volts at idle, no accessories on. switch headlights on, and it bumps up just a tad, as expected. hit the grocery store and then head home - hmm, meter is showing a slow but definite drop in charge - by the time I got home (30 minute drive) it was barely showing 13 volts, and using the turn signal showed a definite twitch in voltage as the signal blinked on & off. Kind of thinking that I need to replace the alternator - again (yes, it has an aftermarket one in there now - about 2 yrs old) and yes, it is one that is supposed to have the "lifetime" warranty. My question is this - is it possible for the alternator to be functioning properly when cold, but slowly lose charging ability as it warms up? from watching the meter, this is what appears to be happening, but I would like confirmation before I go trying to get it replaced. And if this IS the case, then I will definitely need to have things warmed up when I go to get it checked out. Also - could this even remotely be an explanation for my fluctuating idle when the car is fully warmed up (as in after driving for bit)? Edited April 17, 2012 by heartless Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 25, 2012 Share Posted March 25, 2012 My question is this - is it possible for the alternator to be functioning properly when cold, but slowly lose charging ability as it warms up? Also - could this even remotely be an explanation for my fluctuating idle when the car is fully warmed up (as in after driving for bit)? Yes and yes. I've seen them fail in that way before. Electronics can fail due to heat. I've seen at least a few alternators do this as well as a few distributors - car will run for a few minutes and then the spark mysteriously just dies out or will not restart when hot..... What you SHOULD do here is replace that round-plug alt with a 95 to 99 OBD-II alternator. All you have to do is get a plug from a 95 to 99 and splice it to the wires going to your round-plug and leave the yellow wire out of the equation. It's not required on the 95 to 99 unit. These alts were part of a recall campaign and are about $75 from the dealer for the high-quality "Remanufactured for Subaru" units. It's a sweet deal on the best quality money can buy. A Bosch reman for the round-plug style you have now runs about $140 so it's worth the extra work. The newer units are also about 10 amps higher output IIRC. GD Link to comment Share on other sites More sharing options...
heartless Posted March 25, 2012 Author Share Posted March 25, 2012 Thank you very, very much for the info GD - will definitely look into doing the upgrade in the near future, but for now, with money being extremely tight, I am going to be forced into just getting the warranty replacement unit for the one i currently have. As soon as finances allow I will make the upgrade. Link to comment Share on other sites More sharing options...
glkiller2 Posted March 25, 2012 Share Posted March 25, 2012 (edited) like he said yes and yes I had one die in the middle of a 30 mile trip, went to turn a corner and when the car got to idle it started to sputter and died no power. I had drained the battery completely. Got a jump, drove it like that keeping my RPMS up at stops for 7 or so miles. Drove borrowed car to parts store got alternator put it in, no problems since. Mine went fast, Have had them go slow, work intermittently etc. heat is bad:) BTW bench test of old one at the shop said it was good! I am confident the connections were good before I took it out... The shop might hassle ya if it tests ok, BE A BULLY:) get a new one... Edited March 25, 2012 by glkiller2 Link to comment Share on other sites More sharing options...
edrach Posted March 25, 2012 Share Posted March 25, 2012 When you decide to upgrade drop me a PM. I have a number of the square connector alternators. Used from Pull a Part; tested in my Impreza for a month or more and then put on my "spares" shelf for use if one of mine fails (I have a '97 Impreza and '99 Forester) unexpectedly. $40 plus shipping if that works for you. I think it might be time to grab a few cables; don't need them in my cars, but it would be handy for those wanting to do an upgrade. Link to comment Share on other sites More sharing options...
heartless Posted March 26, 2012 Author Share Posted March 26, 2012 Thanks guys, for the validation on this one. glkiller - Since I live 30 minutes from the parts store the car, and the alt will be good & warm when i get there, so it shouldnt be a problem proving it at fault I did call them today cause I couldnt find my paperwork, they have it on record that I bought the thing april of last year. they have to order in another one, should be there tuesday morning, so that is when I am going in for it - no point wasting the gas for nothing. edrach - if you could come up with the cable to go with that alt - i may just take you up on it! older subarus and thier parts are kind of hard to come by up here - dont have any pick-n-pulls in the area, and the yards we do have just dont keep anything from them when they do come in - not enough call for them. (which is why we "stockpile" cheap parts cars) have been having idle issues when warmed up for several months - changed all the usual suspects - CTS, IAC, PCV, vacuum hoses, etc, etc and it still has issues - wouldnt it be funny if swapping in a new alternator cured that little problem as well... oh, and GD - I went and looked them up, my stock alt is 70 amp, the 96 alt i looked up is 85 amp - a nice 15 amp increase would be sweet! i could put the fog lights on the car and not worry so much about burning up the alt like I used to do on the GL! LOL Link to comment Share on other sites More sharing options...
glkiller2 Posted March 26, 2012 Share Posted March 26, 2012 nice:)gl Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 26, 2012 Share Posted March 26, 2012 Yep - 15A is a nice upgrade. If you or anyone else needs a connector a 95 to 99 alt upgrade - look no further than your local yard. Browse for Nissan's. The Maxima's from 86 to 94 have the same connector as the Subaru's from '95 to '99. GD Link to comment Share on other sites More sharing options...
Fairtax4me Posted March 26, 2012 Share Posted March 26, 2012 Some of The infinite wisdom of GD! Thanks for the tip! Link to comment Share on other sites More sharing options...
heartless Posted March 26, 2012 Author Share Posted March 26, 2012 Yep - 15A is a nice upgrade. If you or anyone else needs a connector a 95 to 99 alt upgrade - look no further than your local yard. Browse for Nissan's. The Maxima's from 86 to 94 have the same connector as the Subaru's from '95 to '99. GD um, yeah, another one we dont have around here. this is all farm country and just about everyone drives either a pickup truck, or a minivan/suv kid hauler. Very few "imports" of any kind around here The closest Subaru dealer to me is about an hour away, and they are so small that they only have maybe a dozen cars on the lot at any given time. Link to comment Share on other sites More sharing options...
ivans imports Posted March 26, 2012 Share Posted March 26, 2012 Crapy diodes they never did fix that problem seen it even on old cars sounds like one diode gone makes them charge a bitt low 13-12.75 but still charge barly Link to comment Share on other sites More sharing options...
96LegacyEJ22 Posted March 27, 2012 Share Posted March 27, 2012 Just did this conversion today on the girlfriends car. All the dash lights are now gone! Link to comment Share on other sites More sharing options...
glkiller2 Posted March 27, 2012 Share Posted March 27, 2012 oh no! sounds like maybe forgot to reconnect a lead at batt for fuse box maybe? MAYBE popped a fusible link.... Link to comment Share on other sites More sharing options...
96LegacyEJ22 Posted March 27, 2012 Share Posted March 27, 2012 Oh woops. I meant the battery light and abs light turned off. That's a goos thing Link to comment Share on other sites More sharing options...
glkiller2 Posted March 27, 2012 Share Posted March 27, 2012 lol big dif:) nice job Link to comment Share on other sites More sharing options...
heartless Posted March 27, 2012 Author Share Posted March 27, 2012 (edited) driving to class yesterday evening confirmed that the alt is indeed losing charging ability as things heat up. cold start (car sat for day and 3/4) registered just a hair below 14 volts on the meter. drove to campus - about a 15 min drive, give or take. meter was showing 13.5 volts when i arrived there. no accessories running... Car sat for about an hour while I was in class - exam day, got out early... started car, meter is registering slightly lower than 13.5 volts now... by the time I arrived home again - another 15 min or so drive - it was down to 13 volts even...did have the headlights on coming home as it was heading towards dark thirty. Time to call Advance and see if my replacemnt has arrived yet... (edit to add: I am carrying around an original stock alt from one of the parts cars, and my socket set - just in case) Edited March 27, 2012 by heartless Link to comment Share on other sites More sharing options...
heartless Posted March 28, 2012 Author Share Posted March 28, 2012 ok, so went to see about getting alternator exchanged today - just one small problem - apparently there is nothing wrong with the alternator - it was pushing out 15.5 volts at 2000 rpm, with hi-beam headlights on, and heater blower going full force. (guage only showed 13.5) I was then informed that I had a ground problem. no, aside from the obvious ones - neg cable to trans bell housing & the smaller wire from battery neg terminal to front - where else are there grounds on a first gen legacy? also, what is the best way to unbolt the main neg cable from that stupid bracket off the bell housing?? it just wants to twist. Link to comment Share on other sites More sharing options...
forester2002s Posted March 28, 2012 Share Posted March 28, 2012 Before spending money on this, try cleaning the battery clamps (both -ve and +ve). Yes, I know that the car starts OK, and that headlights etc work OK. But this might be an intermittent ground problem at the terminals. It's worth a try. Link to comment Share on other sites More sharing options...
heartless Posted March 28, 2012 Author Share Posted March 28, 2012 actually - the battery terminals are quite clean (i do stay on top of that), but the chassis grounds are looking kind of rough - the small one right by the battery had some rust build up, as does the big main one. also found the one at the dogbone - that one looks really nasty on the chassis side. Any others I should be aware of?? so I have my work cut out for me tomorrow (no classes at least) The other half did help me get the main one broken free just a little bit ago, using a pair of vicegrips on the bracket to keep it from twisting. Link to comment Share on other sites More sharing options...
Fairtax4me Posted March 28, 2012 Share Posted March 28, 2012 The stupid little ground bracket is held on by the upper starter bolt. Take that out as well and make sure it gets cleaned under there. You might be losing power at the fuse panel. Where does your volt meter draw its power from? Link to comment Share on other sites More sharing options...
heartless Posted March 28, 2012 Author Share Posted March 28, 2012 The stupid little ground bracket is held on by the upper starter bolt. Take that out as well and make sure it gets cleaned under there. You might be losing power at the fuse panel. Where does your volt meter draw its power from? voltmeter is indeed run thru the fuse box so that it turned off with the key. the main ground bracket was off last year when the motor was pulled for resealing, should be good on that side, but i will pull it again just to be double sure - the ground cable side does look a bit on the rusty side however, and that was my main concern for that area. plan is today to get all of them that I have found thus far pulled, cleaned up, a smear of dielectric grease to slow the reformation of rust/corrosion and everything put back together nice & tight. Hoping that will cure the resistance issue. The one person at the parts store that I do actually trust (most there are idiots) showed me how to check for resistance on the ground cable using the DVM on the ohms setting. He says it should be 0.5 or less - mine was well over 8.5 - pushing 9!! cleaning just the small ground from the battery to the body dropped it to about 6.4 - yup, i have work to do. for those that want to know how: DVM (Digital Volt Meter) set to 20K Ohms (touching probes together should show a 0.0 reading) disconnect the battery negative cable and move it away from the terminal. place one probe on the neg battery terminal, and the other on the neg battery cable clamp. Any reading over 0.5 means you have ground problems Link to comment Share on other sites More sharing options...
Cougar Posted March 28, 2012 Share Posted March 28, 2012 (edited) for those that want to know how: DVM (Digital Volt Meter) set to 20K Ohms (touching probes together should show a 0.0 reading) disconnect the battery negative cable and move it away from the terminal. place one probe on the neg battery terminal, and the other on the neg battery cable clamp. Any reading over 0.5 means you have ground problems This is not a correct way to check the resistance of a lead. If the positive cable of the battery is still connected, using this method would allow current to flow in the circuit giving you a big error in the reading. Whenever doing a resistance check power needs to be removed from the circuit under test. When placing the meter leads in series with the circuit as described here the meter should be set to read current. Resistance and voltage checks should be made in parallel across the circuit under test. Also, when checking for low resistance you should set the meter scale to a low scale like 200 instead of 20K. The lower scale gives a better resolution of the reading. A good way to check for a ground problem is to measure across the ground wire in question and check the voltage across it while the circuit is active. Since a good connection will have very little voltage drop across it due to very low resistance there will be very little voltage across it. When measuring the resistance of a wire it should be less than .2 ohms. Edited March 28, 2012 by Cougar Link to comment Share on other sites More sharing options...
Mikevan10 Posted March 28, 2012 Share Posted March 28, 2012 So, Cougar, a good test would be to put a load on the battery (turn on head lamps for example) and then connect one probe of the volt meter to the negtive battery post and the other probe to the engine block? This would test the resistance in the ground cables and the associated connections? Link to comment Share on other sites More sharing options...
Cougar Posted March 28, 2012 Share Posted March 28, 2012 (edited) So, Cougar, a good test would be to put a load on the battery (turn on head lamps for example) and then connect one probe of the volt meter to the negtive battery post and the other probe to the engine block? This would test the resistance in the ground cables and the associated connections? That's correct. It would basically tell you how good the connection is between those points. You could also check the connection to the chassis by moving the probe from the engine block to a good chassis ground point. Since the headlights usually use the chassis for the ground it would be better to check the chassis ground rather than the engine ground using your example. Another good check to make in case you think there is a charging problem is to check the voltage drop between the alternator output and the positive battery post while a good load is on the system. You should hopefully see less than .3 volts across the connection due to standard wire losses. Edited March 29, 2012 by Cougar Link to comment Share on other sites More sharing options...
heartless Posted March 28, 2012 Author Share Posted March 28, 2012 Well, guess i learned something new, too. Thanks for the info Cougar. Hoping that the issue is resolved at this point, i guess only time will tell for sure - driving time. just to clarify a little further - the alt output is the connection that goes to the battery, correct? the single wire with the nut? and one would do this with the meter on the voltage settings? (sorry, i can be a little slow with this stuff, but i am trying to learn) Link to comment Share on other sites More sharing options...
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