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Ok guys, to the point here. In a blizzard right now and having some issues. I have went through three napa batteries in two years on my 1994 Turbo Legacy. The recent one is three weeks old. Sometimes when im driving my seatbelt alarm starts chiming and doesnt stop, even with both belts buckled, it still chimes. I go out thismorning to start the car, nothing. Dead battery. So i jump it from my gfs car, let it charge for ten mins or so, then take off to work a half mile away. By the time i get into the parking lot, all my interior lights are very dim and the abs light came on in the dash. I turned on the windshield wipers to try and clear some more snow, and boom the car died right there. Went to crank it back up and barely turned over and then nothing, just a click. Got it jumped again, let it charge with the cables still hooked up to the other vehicle. Checked the voltage with a meter, showed 13.5. Unhooked the cables, the motor raised in rpms slightly and checked the meter again, showed 12.45 volts. Drove it back home, ( all lights, heater, radio off) and pulled in the lot at my apt and shut it off. Then tried to start it back up, and it cranked over fast just like it should. What is going on?? Sorry if i rambled on, but i tried to detail everything as much as i could.

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bad cables or other charging issue. (intermittent alternator,  slipping belt, etc.)

 

You are gonna need to measure voltage drops at battery, batt pos with chassis ground, batt and chassis ground to starter terminal, etc. while cranking as well as for bad grounds. internally corroded cables, etc.

Edited by 1 Lucky Texan
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Ok so i went out again, started up fine. I took it for a drive, but i noticed when i turned on the headlights and the heater the clock light on the radio got really dim, as did the gear indicator on the dash.

Measured the voltage between, the neg post and the engine block and the tranny case, and it showed no voltage. 

 

I measured running voltage between neg a pos. posts again, with heater on and headlights on, showed 11.9. With heater and headlights off, showed 12.9 volts. 

 

I did notice the negative battery cable clamp had been broken at the bottom, and had been jimmy rigged back together.

 

Before i go throwing parts, is there any other definitive test i can do to rule out either the cable and/or the alternator?

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I suppose there is a chance of rodent damage, but i highly doubt it. It seems almost to be an intermittent charging problem, could the jimmy rigged neg cable be an issue? Also if i go to the parts store, im sure they arent going to have a custom fit cable, so will a universal top post cable in the right length be ok?

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yes, just make sure you get the correct length.  All my Subarus get Marine post battery terminals and I use marine battery cables, they seem to last longer than the automotive ones.  You'll end up with a ring to ring Negative cable that will for the 12mm bolt that holds it down @ the upper starter bolt bracket and then the other ring fits directly over the marine post (terminals will have wing nuts) 

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Before i go throwing parts, is there any other definitive test i can do to rule out either the cable and/or the alternator?

 

Measure voltage at the alt. or remove it for testing at the parts store.

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sounds like what everyone else is saying, bad alt

 

at idle, what is the alternator voltage output (the covered terminal on top of the alt) referenced to chassis with some loads (headlights on, heater fan on).  compare that with the positive post reference to chassis and the negative post.

 

with a single jumper cable, clamp one end on the negative battery terminal (make sure there is no corrosion between the clamp and the post) and the other end to a good metal contact on the block.  see if voltages improve any.  have to decide whether you have one or two problems (intermittent connection at the negative terminal and/or a bad alt).  

 

alternatives to the parts store alternator if you can swing it

 

http://www.ultimatesubaru.org/forum/topic/110564-1993-legacy-charging-system-alternator/

Edited by 89Ru
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Bad alternator or bad/intermittant grounding would be my thoughts. The flakey negative cable connection would be the first thing I fixed. Do that and recheck the voltage while running. If it's still that far below 14 then it's the alternator.

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It is pretty obvious that the battery isn't getting charged for some reason. The alternator may be bad but there could be connection problems with the alternator and battery causing the problem. From what you stated about the warning lights and other things it makes me think the alternator has some bad diodes inside it. Have the alternator output checked to see if that is ok and also check the AC voltage across the battery while the engine is running around 1,500 RPM. There should be no more than .1 volt of AC voltage if things inside the alternator are okay. You should also have around 14 volts DC at the battery while there is a pretty good load on the system. You are most likely going to need a replacement alternator. If the AC ripple voltage is really bad that would explain the short battery life problem you had. 

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Ok so today took the battery out and took it to NAPA to have them charge and check it. Left it for a while, showed back up and they said it was bad, wouldnt hold the charge. This batt was only a month old, bought it february 4th. They warrantied it, got the new one, along with a new 4 ga. negative cable. Installed the new cable and battery, cleaned all connections, tightened, etc.... Cranked and started just fine. voltage showed 12.3 with headlights, heater, and radio on. Showed 13.0 with everything off. I guess its time to swap the alternator? Should i drive to the parts store and have them check it before i swap? And do you have any preferences when it comes to which parts store to use for alternator? Thanks again for all the help. 

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Pull the alternator and bring it in with you, as cougar said it sounds like it has failing diodes parts stores generally don't check for ac ripple so when you have them test it ask what the ac output was. If they say it is charging fine and has no ac ripple then I would start looking at your wiring.

Edited by mikaleda
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Before you pull the alternator check and see if your parts store can test it while it is out of the car.  All of the parts houses around me NAPA, AutoZone, O'Rileys, and Carquest can't.  But I do have a alternator rebuild shop that can that is only 30 miles away. 

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You stated in post 16 that the engine was at idle speed when you made the voltage measurements. From what you say the results were it doesn't seem too bad. You should rev the engine to around 1,500 RPM, turn the headlights and blower on high and then check the voltage at the battery. Hopefully you will have around 14 volts present and that would be good. Check the AC ripple voltage at the same time you are doing that and see if that is below .1 volt, as it should be.

 

If you don't already own a voltmeter to test with I highly suggest you invest in one since you can get one at a very reasonable price nowadays. Having a meter and a factory service manual for the wiring.....priceless.

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Stupid question here,  but if the alternator is going bad wouldnt the batt light come on in the dash? It comes on when the key is on the on position, so i know it still works. 

 

Usually that light will not come on until you have a total failure.  When my alternator started to go out the light never came on. 

 

They don't call it a "Idiot Light" for nothing. 

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Usually that light will not come on until you have a total failure.  When my alternator started to go out the light never came on. 

 

They don't call it a "Idiot Light" for nothing. 

 Thanks, thats kind of what i was thinking. Im off to the parts store, i'll post back with hopefully good luck later. Thanks again to everyone. 

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While your at the parts store I suggest you purchase a good digital meter or DVM. Using it you could look at the output voltage of the alternator and establish for yourself if the unit is bad or not. For around 40 dollars it would be one of the best tool investments you could buy. A number of parts stores carry the Innova Equus meters. They are designed with the automotive repair in mind but are certainly ok to use on anything electrical.

 

Here is a link for one of their models.

http://www.equus.com/Product/3320/Auto-Ranging-DMM   

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got the multimeter, got the new alternator. Took as long to drive to get the alternator as to put it on. Got it all installed, started the car, checked voltage at the pos and neg posts, showed 14.08. Then tested between the batt post and alternator post showed 14.12, both with no load.

Testing with a load, (head lights, heater, radio,) showed 12.95 at both places. Both were tested at idle. 

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