garner Posted January 11, 2005 Share Posted January 11, 2005 My Brat is driving me a little crazy.... Here's the deal: New alternator (less than 600 miles) New Battery (about 800 miles) Both have been tested by two Auto Parts stores, out of the car. Battery dies while driving. I mean, the motor starts to miss, lights dim, dash lights dim, etc.... I've been doing some scientific monitoring of the battery voltage at various stages Here's a time line and battery voltage(s) Taken with a digital multi tester off the alternator, possitive on large bolt down possitive lead, negative to body of alt. Key in "OFF" Sun 12:00 midnight 12.96 volts Mon 8:00 am 12.94 volts Mon 7:00pm 12.93 volts Run for 20 minutes 12.15-12.40 volts, bounces around, voltage drops under quick revs but settles back up to mid point Mon 7:30pm (shut down) 12.70 volts Mon 8:00pm 12.71 volts Mon 8:30pm 12.72 volts Mon 9:30pm 12.71 volts Tues 9:30am 12.65 volts This was all done at a stand still in the garage. If I drive like out to mudrat's and back (15-20 miles) and make a couple stops, I can barely get home, starts to miss and act funky about 1-2 miles from home. Do these voltage drops seem out of line to you? Shouldn't voltage off the alt while running be higer than 12 volts? Shouldn't the voltage off the alt go UP while at higher revs? Is there something I'm missing? WTF is my problem? garner Link to comment Share on other sites More sharing options...
torxxx Posted January 11, 2005 Share Posted January 11, 2005 sounds you got a bad connection somewhere in the charging wires.. you get driving and the wire shorts out, stopping the alt from charging the battery. The voltage off the alternator should be up to 14.4 volts I believe.. car battery runs at 13.4 Vs so only charging 12 volts would make the battery slowly die. quick revs means more spark, more volts used off the battery, thats why its dropping when you quick rev. Link to comment Share on other sites More sharing options...
Vanislru Posted January 11, 2005 Share Posted January 11, 2005 I think the output from the alt should be around 14v, is this and ea82 alt in there? I think your alt isn't charging the battery cause it does run for a bit meaning there's something of a charge in there that will stay until drained, but it's not being kept up by the alt. Don't know if this makes sense I'm a little out of sorts right now. My 2cents your alts toast, possibly diodes. Link to comment Share on other sites More sharing options...
Cougar Posted January 11, 2005 Share Posted January 11, 2005 The voltage readings you took while the engine was running seem low. You should see between 12.7 and 14.8 volts with the RPM's around 2000. There may be a problem with the connection between the battery and the alternator or the field connection. Also check the battery connections. It wouldn't hurt to clean them even if they look ok. If that has already been done then fine. Take a voltage measurement between engine ground and the alternator output lead. Also measure the voltage of field wire connection on the alternator. Have the engine running around 2,000 rpm when you do this. Also have the headlights on high along with the blower motor set to high to make a decent load to the alternator. Let us know what you read for voltage. Edit: Going by the readings you took after starting the car on Monday evening it does seem the alternator is not producing a sufficient charge. The battery voltage should have gone up after you started it but instead it dropped. Checking those points I mentioned will tell the story. Link to comment Share on other sites More sharing options...
garner Posted January 12, 2005 Author Share Posted January 12, 2005 Hey I geuss I can say I have an Electric/Gas hybrid!!! Only 20 miles per charge is not great though. actually, it occurs to me, I might not be looking at the rght connectors on the alt. (yes EA82T alt) I've got 4 wires on the Alt: 1.) large held on with a nut (white in my case) possitive going to the starter/tying into the battery possitive (my battery is relocated in the back of the Brat) 2.) large Black held on with a nut going to Neg of battery 3&4.) are in a connector T shaped heavy black on top, light white with red on bottom Which wire is providing the charge? garner Link to comment Share on other sites More sharing options...
Cougar Posted January 12, 2005 Share Posted January 12, 2005 The large white one is the alternator output lead. The field lead is the red one I think and the light white is for the warning light. Measure the voltages on the output lead, the red one, and the light white wires as I suggested in the last post. They all should measure close to the battery voltage with the engine running. Link to comment Share on other sites More sharing options...
bratsrus1 Posted January 12, 2005 Share Posted January 12, 2005 Hey Garner This is Jerry, if you are talking about your 79 brat then there is a fuse well 2 or 3 of them under the glove box. One of them has to do with your charging system. I had a 78 brat that drove me nuts until i found that fuse, it was shot a 5 amp fuse. I don't know why subaru put it there but it's there. Hopes this helps you. Thanks Jerry Link to comment Share on other sites More sharing options...
garner Posted January 12, 2005 Author Share Posted January 12, 2005 Glenn, The field is the heavy wire a the top of the T right? And it should bring battery voltage in to energize the field correct? And just to make sure I am conceptualizing the function of the alternator feild, it is basically a current that generates an electro-magnetic force that allows the alt to generate power? I tested a bunch of stuff last night. I can confirm that the battery is not draining and that the charge from the alt is not sufficient. I'm seeing no rise in voltage off the Alt at any rpm, infact it goes down consistently, until I let it idle, then it creaps back up to about where I started. Thanks Jerry, actaully during the swap, all my charging wiring was swaped to the EA harness, but I should have a look for these rouge fueses you speak of This is so strange because I have really not done anything to the charging system since I installed the motor, I can't believe I've been able to put 600 miles on it without issues..... One question/thought: In the research I've done, it seems the "charge indicator light" is somehow in the cirquit and is more important than just being an "idiot light" ? My connector is connected to the alternator but not to any dash light? Could this be a problem? Could it allow everything to work fine for a couple of 200 mile trips (to WCSS6 and back) but slowly cook the alternator? garner Link to comment Share on other sites More sharing options...
archemitis Posted January 12, 2005 Share Posted January 12, 2005 i have bought "new" alternators that were in worse shape than the ones i was replacing. several places tested morganms alt and told him it was fine. swaped in a junkyard alt, and it fixed all the problems. sounds like an alt to me. Link to comment Share on other sites More sharing options...
torxxx Posted January 12, 2005 Share Posted January 12, 2005 k of This is so strange because I have really not done anything to the charging system since I installed the motor, I can't believe I've been able to put 600 miles on it without issues..... One question/thought: In the research I've done, it seems the "charge indicator light" is somehow in the cirquit and is more important than just being an "idiot light" ? My connector is connected to the alternator but not to any dash light? Could this be a problem? Could it allow everything to work fine for a couple of 200 mile trips (to WCSS6 and back) but slowly cook the alternator? garner Yes it is possible to slowly cook the alternator. When I make my trips down to Anchorage (375 miles) I've cooked 3 out of 4 alternators. Its weird, it will make it all the way down there, and then its after the car as cooled down, that the VR in the alt goes out. I still havent figured out what makes it do that. I can drive all day every day in the city, but as soon as I make a road trip, I blow an alt.. Link to comment Share on other sites More sharing options...
Cougar Posted January 12, 2005 Share Posted January 12, 2005 Garner, The large wire that is held on by a nut is the alternator's output wire. Not the field wire. This wire has to handle the large amount of current needed to supply the battery. It is tied to the positive battery connection and is always hot unless the battery is disconnected. Never get a ground connection near this lead. The field wire supplies voltage from the battery to excite the field windings which builds up a magnetic field that the rotor windings pass through and generate the power. The three phase AC voltage is rectified through the diodes and regulated to charge the battery. I think it is the light white color wire but not sure. You are correct about the warning light. A lot of systems use this light in the field circuit. If the light is out, or has a bad connection in the path then the field will not work and and there is no output from the alternator. A good check for proper operation is when you turn the key to the 'run' position and check the warning lights. If the light turns on then things are working ok in the circuit because current is flowing and turning the light on. The other small wire is for the regulator circuit. Please check the voltages on these wires as I stated in my last post and let me know what the readings are. They all should be close to the battery voltage with the engine running. Link to comment Share on other sites More sharing options...
garner Posted January 12, 2005 Author Share Posted January 12, 2005 I don't remember the exact voltages last night but the current out of the alt and the field current in were nearly identical (within a couple of .01s) with the engine running and very close to battery voltage. This was with both the field lead and the warning lamp lead disconnected. I forgot to turn the headlights on high etc to generate a decent load..... Should the field voltage fluctuate or be constant battery voltage? With my wacky harness swapping action involved with my set-up, I have the charge light in the dash from the origional harness and the connector from the EA82T harness connected to the alt but the two are not connected, does that make sense? I need to make that connection just in case it is the source of my problem. I suppose I could also just rig up a warning light under the hood to make sure the field cirquit is complete... I'll do some more head scratching and maybe a little less and see if I can figure anything out tonight.... It sure seems like it has to be the ALT but I really don't want to go to the auto parts house to have it test ok again. garner Link to comment Share on other sites More sharing options...
Vanislru Posted January 12, 2005 Share Posted January 12, 2005 The field voltage should be constant bat volts. The field sets up just that, the magnetic lines of force in the alt that the windings cut through generating your three phase ac which is then rectified by the 4 diodes circuit in the alt to dc. No field no output from the alt, that's why you can't jump a sube with a completely dead bat. Link to comment Share on other sites More sharing options...
Vanislru Posted January 12, 2005 Share Posted January 12, 2005 What kind of test are the auto shops doing, just testing the windings? Link to comment Share on other sites More sharing options...
garner Posted January 12, 2005 Author Share Posted January 12, 2005 What kind of test are the auto shops doing, just testing the windings? Just the put it on the machine kind of thing (out of car) I don't really know how good and accurate these tests are... garner Link to comment Share on other sites More sharing options...
Cougar Posted January 12, 2005 Share Posted January 12, 2005 Garner, I assume the charging system was working, as it is, at some point in time. If you don't have the warning light in the circuit you may not need it, but it would be good to know when there is trouble with the system so you should get it connected. The tests you did while the connector was removed from the alternator don't really help diagnosis the problem that much. Check the voltages with everything connected as it should be. If either of the two smaller wires on the alternator are not close to the battery voltage then you need to check for a problem on the wire(s) that read low. If the volt readings are close to the battery voltage and the alternator output voltage isn't at least 12.7 volts with the headlights and blower on high and engine running at 2k rpm, then replace the alternator. Link to comment Share on other sites More sharing options...
rallyruss Posted January 12, 2005 Share Posted January 12, 2005 12.66 is a good voltage for a fully charged batt. a little over is usually a residual surface charge. no big deal. alt. out put to charge the battery and run the vehicle should be between 13.5 and 14.5 +or- a little. it may drop lower if it cannot keep up with demand say at idle with too many loads on or a discharged batt. cougar is right about checking voltages at the back of the alt. you want to see what you have at the conecter and at the main power lead. yes the charge indicator out or missing can keep a alt. from charging. the testers at the parts stores are rather acurate. if it tested good there you have a wiring problem. may sound stupid but you checked the grounds to the body and the motor right? did you tranfer the fusible links to the bratt too there are two for the alt. Link to comment Share on other sites More sharing options...
Snowman Posted January 12, 2005 Share Posted January 12, 2005 Do you have a spare alternator that you could throw on. My mom's legacy did the same thing and it was something inside the alt. Link to comment Share on other sites More sharing options...
garner Posted January 13, 2005 Author Share Posted January 13, 2005 OK did some more scientific testing last night and I think, perhaps, I've determined the Alt is indeed bad. Here is the test proceedure that I performed: remove the ALT output lead to isolate the voltage off the stud (ie to be sure the voltage I was seeing was not off the batt) tested voltage in 3 locations: 1. Battery/Alternator output lead (I will refer to this as BAL) 2. Alternator Output Stud (AOS) 3. Field (tested from the back while connected) tested in 3 states, Off, Running, and After Running Off: BAL=12.96v(this was after a breif charge to get the batt into the 12s) AOS=12.39v (this seems wrong to me, why voltage out the stud with the car off and the battery disconnected from the alt? Field=12.96v (perfect) Running: BAL=12.45v AOS=11.93v (went down slightly with higher RPMs) Field=12.45v (again, perfect) Off After Running (about 5 min) BAL=12.81v AOS=12.25v(again, why voltage out the stud with the key off and batt disconnected)(after recennecting to BAL, voltage=12.81 Field=12.81v Conclusion: I am really only puzzled by why there is voltage present on the Alternator Output Stud with the key off? I am guessing there should not be voltage leaking from the feild to the output stud? I'm going to the parts house tonight after work, if this freekin thing tests out good, I'm going to What thinkith ye? garner Link to comment Share on other sites More sharing options...
Cougar Posted January 13, 2005 Share Posted January 13, 2005 Garner, I suspect that some of the diodes are bad in the alternator and that is why the voltage is low. Full output can't be produced if some are bad. If you had a O-scope you could look at the output waveform. The main output lead of the alternator is tied to the positive battery post. The other leads are tied to the battery indirectly. The voltage you saw was being backfed from one of the other leads you had connected to the alternator. That kind of test doesn't really mean much. The real test is having all the leads connected normally and checking each of the voltages then. They all should be over 12.7 volts with the engine running around 2k rpm. A new alternator should fix you up fine. Link to comment Share on other sites More sharing options...
ausubaru92 Posted January 14, 2005 Share Posted January 14, 2005 In an ea82 car,... the Black/White & the White wires from alternator come from alt then to the fuseable links and then to battery. The White/Red goes to fuse box then to dash for the Warning light The ea81 alt, White goes to Battery. Black & White/Black & Yellow go to regulator. and thats all i know Do u have fuseable links,. check these. IMO, The warning light should not affect charging From your alt. Thick white to battery via fuseable link (marked 1.25, i doubt this is amperage rating, prob wire gauge) Black/White from T connector to fuseable link marked 0.5 (same reason as above) then to battery. White/Red to fuse (15amp) then to Warning light... (which i assume is grounded) Hope this shines light on your problem:D Link to comment Share on other sites More sharing options...
rallyruss Posted January 14, 2005 Share Posted January 14, 2005 IMO, The warning light should not affect charging White/Red to fuse (15amp) then to Warning light... (which i assume is grounded) Hope this shines light on your problem:D well I could be wrong but most all vehicles I have worked on rely on the light as a integral part of the charging system. no light or fuse for light no charge. as a side note it really pisses off the mechanic that changed the alt with no luck and then I come along and reinstall the missing fuse (no I did not remove it) . he had the harness all apart with almost half a day into it. ahh good times. Link to comment Share on other sites More sharing options...
Cougar Posted January 14, 2005 Share Posted January 14, 2005 Right on Rallyruss! You are correct. Without that light, you have no field voltage to the alternator. Not all systems do it this way I suppose but most do I believe. Link to comment Share on other sites More sharing options...
garner Posted January 14, 2005 Author Share Posted January 14, 2005 Thanks AUsubaru, you've confirmedwhat I've figured. The 85 FSM is very vague about wiring and especially wire colors, but you have described my wiring perfectly. As for the light, I have never had on connected in this set up and I have put 500 perfectly sucsessful miles with no charging problems. In my research, it does seem the charge light is important/crucial to the circuit (I had no idea at the time I did the swap and all the wiring). I cannot figure out how things could work for 500 miles and not now.... Had the Alt checked again last night at two parts houses. One had the new generation touch screen computerized tester, the other was old school analog....Both showed 14.5 volts off the alt. How does the field influence charging out put? Is it's voltage in constant battery voltage or does it raise and lower to adjust output voltage? I have consistant Batt voltage coming in via the field but it seems not to vary with engine speed. This is again, without a charge indicator light connected. On a related note: Is it the alternator that controls the on and off operation of the indicator light? or is it somehow controled through the ECU. Just trying to understand the circuit and figure out how the light comes on with the key in the "on" possition and shuts off once the engine is running/alt is charging. One interesting thing I discovered last night: I checked codes from the stock ECU and got a code 13 (starter switch in on possition) I don't know that this is really any clue but it did give me something to think about. I'll track that down tonight. It makes me wonder if there isn't a problem with either the ignition switch, which is certainly a bit suspect anyway or maybe the "on" and "start wires are crossed or shorting to each other. Maybe there is just an extra drain form the starter circuit while running??? We'll see. I'm tempted to just totally rewire the charing circuit from end to end. It may take that, but I'll save it for a last resort. Thanks for slogging through this with me, certainly not one of my favorite topics to troubleshoot and post about. garner Link to comment Share on other sites More sharing options...
Cougar Posted January 14, 2005 Share Posted January 14, 2005 Thanks AUsubaru, you've confirmedwhat I've figured. The 85 FSM is very vague about wiring and especially wire colors, but you have described my wiring perfectly. As for the light, I have never had on connected in this set up and I have put 500 perfectly sucsessful miles with no charging problems. In my research, it does seem the charge light is important/crucial to the circuit (I had no idea at the time I did the swap and all the wiring). I cannot figure out how things could work for 500 miles and not now.... Had the Alt checked again last night at two parts houses. One had the new generation touch screen computerized tester, the other was old school analog....Both showed 14.5 volts off the alt. :banghead: How does the field influence charging out put? Is it's voltage in constant battery voltage or does it raise and lower to adjust output voltage? I have consistant Batt voltage coming in via the field but it seems not to vary with engine speed. This is again, without a charge indicator light connected. On a related note: Is it the alternator that controls the on and off operation of the indicator light? or is it somehow controled through the ECU. Just trying to understand the circuit and figure out how the light comes on with the key in the "on" possition and shuts off once the engine is running/alt is charging. One interesting thing I discovered last night: I checked codes from the stock ECU and got a code 13 (starter switch in on possition) I don't know that this is really any clue but it did give me something to think about. I'll track that down tonight. It makes me wonder if there isn't a problem with either the ignition switch, which is certainly a bit suspect anyway or maybe the "on" and "start wires are crossed or shorting to each other. Maybe there is just an extra drain form the starter circuit while running??? We'll see. I'm tempted to just totally rewire the charing circuit from end to end. It may take that, but I'll save it for a last resort. Thanks for slogging through this with me, certainly not one of my favorite topics to troubleshoot and post about. garner The battery sense voltage changes as the battery does. When more load is applied to the battery and the voltage goes down, the field voltage will increase causing the alternator output to go up and compensate for the drop. If a problem happens internally to the alternator then the lead for the light goes toward a ground level and turns on the light. When things are normal, the light is not grounded through the alternator and it stays off. When the key is turned to the run position the light will turn on because the alternator is not charging. This is a good check for the proper operation of the light circuit. When the alternator was checked, I assume they had a good load tied to it while under test, producing a lot of current, and the output wasn't just floating. Reading your previous posts it seemed the regulator and field voltages were ok and the output was low. You may have to get this checked out while installed in the car by a pro, but it sounds to me that the alternator may be bad. If the alternator had a good load on it when it was tested then it appears there is still a problem in the vehicle. Link to comment Share on other sites More sharing options...
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