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Old 04-27-2009, 07:08 AM   #1
britimp
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Default Battery or Alternator problem

Hi, when driving the other day the stereo started flashing on and off, the ABS light came on and the AT oil temp came on too. The car seemed to be struggling so I headed home. Got it into the drive way and switched it off. Tried to start it again and it was like the battery was half dead. The lights came on but it would not turn over.

Pulled the battery off our Impreza and it ran fine. Charged the Legacy battery over night put it back and again its running fine. Checked, cleaned and rechecked all the connections and the alternator belt looks tight.

Got to work this morning and put a DVM on the battery with the engine running, voltage is slowly dropping from 12.46V to 12.41V in a couple of seconds - I figure the output from the alternator should be around 14V. Also put a load tester on the battery that says its good.

Is my alternator toast and why is my battery/alternator warning light not comming on?

Any ideas?
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Old 04-27-2009, 03:23 PM   #2
Pow_Pow_BCC
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Changing your alternator should fix your problem. With a DVM on your battery while running the alternator should keep the voltage over 13v i believe, none the less it sounds like your alternator.
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Old 04-29-2009, 07:57 AM   #3
britimp
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I'm thinking the alternator too. I ran through the diagnostic flow chart from the FSM and the charging system checked out fine, all the numbers were bang on.

I cleaned all the contacts and battery terminals and thought I'd solved it but it did the same thing last night. I was pottering around town doing errands - lots of stop start driving at low revs - and the stereo went out followed by the speedo and rev counter but again no charge warning light. I took it for a short thrash on some back roads and it ran fine after that and sarted up again ok in my driveway later.

I think my battery might be garbage even though it passed a load test.
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Old 04-29-2009, 10:37 AM   #4
runninstrong
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Could be the battery, but it's been pretty warm around here. Usually the cold weather exposes the battery's weakness if it's on its way out.

You cleaned your contacts, so I'm assuming you checked your cables for any exposed wire, excess corrosion near the female terminals of the cables? That is usually what happens when my cables start to corrode up.
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Old 04-30-2009, 07:16 AM   #5
britimp
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Its funny you should mention the weather, all this only started happening when it suddenly got warm around here!

Its all pretty much cleaned up and tightly snugged. I am going to test the electrolyte today and give it another load test too.

I am also going to start looking for loose connections elsewhere but I really don't want to start unravelling the wiring harness - it might be time to pass it on to a professional!
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Old 04-30-2009, 08:04 AM   #6
Jonathan
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Short circuit somewhere ?

If you leave the car sitting, doing nothing for a few days will the battery still be good ?
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Old 04-30-2009, 08:16 AM   #7
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Just tested the electrolyte, its in the "fair" range on the hydrometer. I've put it on charge for 20 minutes and will test it again.

I will investigate the short circuit possiblity - I put a new stereo in it when I bought the car and something may have come loose back there.

Thanks for the help and advice I'm getting.
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Old 04-30-2009, 03:11 PM   #8
mikeylinden
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Ok, so quick test for the alternator, start the car let it run for a min or two, disconnect the negative battery terminal, if the car continues to run then the alternator should be fine. You could try driving it around the block or something with it disconnected. Be sure to secure the terminal to something first though so it doest go flapping around. I just did this the other day to my legacy because i have one battery for 2 cars right now and didn't feel like carrying it across the yard haha how lazy can i be.
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Old 05-01-2009, 07:26 AM   #9
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Sounds like its worth a try - I really don't want to have to buy a new alternator right now.
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Old 05-01-2009, 07:37 AM   #10
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Ok, so I just disconnected the negative terminal from the battery with the car at idle - it died instantly.

New alternator?
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Old 05-01-2009, 10:06 AM   #11
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Thats what it sounds like to me. Unless they made major changes to the charging system between 95 and 99. The low voltage the alternator is putting out seems kinda supicious as well. As far as my experiences go i havent seen lower than like 13.5v on a working one. Sorry dood
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Old 05-01-2009, 10:11 AM   #12
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your car should not continue to run after disconnecting the negative cable. that is down right stupid thinking. All cars will shut off after disconnecting the negative cable.
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Old 05-01-2009, 10:12 AM   #13
britimp
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I'm going try and put a tiny bit more tension on the belt and run through the FSM diagnostic test once more to see if I can pep up the charge voltage.

Looks like its time for a new alty.

Thanks to everyone who replied!!!!

By the way, anyone happen to now what the output current of the alternator should be at idle?
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Old 05-01-2009, 10:43 AM   #14
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Quote:
Originally Posted by turboL View Post
your car should not continue to run after disconnecting the negative cable. that is down right stupid thinking. All cars will shut off after disconnecting the negative cable.
Not trying to be a duche here, but i did it the other day, not only did it run, BUT I DROVE IT! WITHOUT A BATTERY!! imagine that. It depends on the way the system is wired, some will shutoff, yes but the engine essentials run from the alternator. Running from the battery is dumb, think about it, constant charge, drain cycle on the battery, have fun buying a new one every couple months.
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Old 05-01-2009, 11:04 AM   #15
turboL
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you had to have taken off the positive cable, even then I am still suprised it ran well.

Without a negative cable on the battery, NO system in the car can work. Its simple electronics. You need a source, a load, a conductor, and a ground. Take away the ground and no current can flow, i.e. nothing will work. I wont believe you until you come to florida and show me.

Taking off the positive cable also isn't to bright. Batteries, act as somewhat of a voltage regulator (along with the actual voltage regulator).
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Old 05-01-2009, 12:18 PM   #16
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Hey man, im not gonna lie, ive never personally ripped apart a subies electrical system on a count of ive never had the need. All i know is that it works. I will GLADLY post a video of me doing it.
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Old 05-01-2009, 01:43 PM   #17
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if i go outside and do this to my swapped legacy, ill be humbled.
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Old 05-01-2009, 04:17 PM   #18
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im humbled. but i can see why it works. current has to get to ground somehow, its that simple. When you take the negative cable off, which i just did 5 minutes ago, that current backfeeds through other circuits to the battery. its not good, but it works.
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Old 05-01-2009, 09:54 PM   #19
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Quote:
Originally Posted by turboL View Post
you had to have taken off the positive cable, even then I am still suprised it ran well.

Without a negative cable on the battery, NO system in the car can work. Its simple electronics. You need a source, a load, a conductor, and a ground. Take away the ground and no current can flow, i.e. nothing will work. I wont believe you until you come to florida and show me.

Taking off the positive cable also isn't to bright. Batteries, act as somewhat of a voltage regulator (along with the actual voltage regulator).

I'm in Florida and I can drive my Legacy around with the negative cable disconnected on the battery~

EDIT: Aw Shucks, nevermind.
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Old 06-16-2009, 03:02 PM   #20
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Default A similar issue

I had what sounds to be a similar issue with my 2004 STI. Driving on the highway in the rain at 80mph (didn't say where). The whole car started bucking like the fuel was intermittently being shut off, ABS and most other warning lights were blinking / dimming. At the time I was using the lights, the wipers (on int) and the AC to un-fog the windshield. The car then just shut off. I quickly puched in the clutch, and pulled off the road. I thought it was my alternator since it wouldnt start. I waited 10 minutes after poking around, and tried again then it started. I had the battery load tested and it was fine (Orig 3yo Subaru Battery). Did the pull the wire test and the alt was fine as well. Couldnt explain it, bought a yellow top next day. I havent had it happen since, but I do notice on my voltage gauges a large drop when i turn on the AC. It goes from 14.6v down to almost 11v sometimes, but 12.5v on a regular basis, with nothing else on, just AC. When the wipers are on intermittent with the AC and lights it makes me think the car will likely die again from the noises it makes (sounds like deep engine idle and loud fans). Took it to the dealer they couldnt pinpoint the problem, and claim I installed too many things into the electric for them to take blame. Now i only use AC when on the highway with no issues.
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Old 06-16-2009, 10:28 PM   #21
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You have to replace an alternator. My car was 2001 and it had intermittent with recharging for a few weeks until it went. It took me only 20 min to do and the problem had never come back.
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Old 06-17-2009, 07:06 PM   #22
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i just went through this yesterday, it was on a chevy but same things going wrong. dash lights coming on and speedo not working. replaced the alternator and the battery and the same thing was going wrong, figured we got a bunk alternator and took it back out to take it back and realized the power wire that you bolt to the alternator broke at the starter solonoid so really it wasnt the battery or the alternator.
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Old 06-18-2009, 11:17 AM   #23
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Quote:
Originally Posted by turboL View Post
your car should not continue to run after disconnecting the negative cable. that is down right stupid thinking. All cars will shut off after disconnecting the negative cable.
This is an old trick for old cars. You could do it on cars from the 1950's, but I'd be worried about doing this on a modern car full of ecu components. Just like they say not to jump a modern car like you used to 40 years ago. My guess is the auto companies are worried about voltage spikes caused by stupid people doing things out of procedure?!? I can't see how a jump start done properly could hurt the car...

Anyway, don't forget that once your battery has been run all the way down, you've shortened its life. This is why a bad alternator can wind up turning an older battery into a bad battery, too. Lead acid batteries should never be run close to dead, due to their design.
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Old 09-28-2014, 06:03 PM   #24
johnnyidaho
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Default Alternator Issue

I just purchased a 99 Subaru Legacy AWD for my son and when he drives the car it slowly dies indicating a alternator issue. Problem is the alternator is brand new as the last one smoked (per previous owner) and he bought a new one and installed it himself. I checked the belt which feels tight and spins the drive on the alternator when running. I put a test light on the ground on the alternator and touch one of the two leads which come off of the plug and got a light but the other lead doesn't light. Any thoughts would be welcome. thanks in advance.

Continue to troubleshoot this as follows; engine running voltmeter reads 15.30-15.45 on battery leads, engine off voltmeter reads 12.75 on battery. Currently charging battery. Noted that the plug for the alternator is not seating correctly and not locking in place. Believe that alternator may be incorrectly sized to receive this plug. Also plug is cracked as well.

Lastly, when running the car and plug inserted in alternator, battery warning light on dash is on as well as brake light. Once plug is disconnected both lights extinguish??

Thanks in advance.

Last edited by johnnyidaho; 09-28-2014 at 07:07 PM.
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Old 09-30-2014, 07:33 PM   #25
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classic symptoms of a failed voltage regulator. I believe Subaru uses one built in to the alternator. The previous owner who claims to have replaced the alternator with a new one, can you get a receipt and get a replacement under the warranty on the part?

The output voltage is way too high and will cook your battery and burn out lights until it is fixed. I would take the alternator off and get it tested. As to the brake warning light; it could be a great many things. Perhaps it is related to your electrical problems, perhaps it is a real problem and the light being off sometimes is an electrical issue. See what happens after you get the alternator sorted out. If the alternator tests good, I would then look at the harness and plug, testing for continuity and the like.

Last edited by CrankyOldGuy; 09-30-2014 at 07:35 PM. Reason: spelling
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