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Old 09-27-2015, 06:15 PM   #1
Ceh92
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Default Battery being drained, can't find source.

Alright, I have been reading around and as a result of not figuring this out I am posting this.

I have a 2003 WRX that is mildly modded. It has a yellow top Optima battery and a rebuilt alternator according to the previous owner (one of the diodes went bad).

I am in the military and in training so I only get to drive on the weekends, so the car sits all week. One week about a month after I got the car I went out and the battery had been drained just enough that it couldn't turn over the engine, but not enough so my gauges and lights still worked. I got a jump, drove around to charge the battery and the next week the same thing. So I bought a battery charger and charged the battery completely over night and went to auto zone to get the alt and battery tested, both passed the in car test.

Since then, I took out my multimeter and did a few tests. First, I did a test to find if there is a draw on the battery. Unhooked the ground, with positive lead on the connector and negative lead on the terminal and measured the current when the car is completely off how it would sit the whole week. The measurement was 10ma of current being drawn which I understand is reasonable. With the car shut off, battery measured 12.3 volts, at the B+ on alt it was around 12.5 volts. While the car is running I'm getting 13.5 volts at the battery.

All of these numbers seem right, but the issue that I think may be the problem is the battery light is not coming on when I turn the key to the "on" position (engine not running). I read that this light provides an excitement charge to the alternator, so I am wonder what could cause the light not working. I pulled the gauge cluster and the bulb is soldered in, so I wouldn't know how to replace it. I also tried grounding the black and yellow wire on the green plug on the alt and still no battery light.

I just got all these numbers today and fully charged the battery for all these tests today, so I will go get some readings tomorrow and see if somehow the problem was resolved, though if it was IDK what it could have been.

A few other things, I have an aftermarket radio and gauges (boost, afm, oil psi) but all of those fully power down, and like I said I did some tests and not current is being drawn off of the battery the way the car usually sits for a week (only 10ma).

Thanks for any help and advice.
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Old 09-27-2015, 08:01 PM   #2
Ceh92
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Alright, less than 8 hours later I go to do some more tests, the ripple test and a current leak test, both were inconclusive. However, I tested the voltage at the batter since the car had been sitting: 12.3v then I start the car up and check the voltage, dropped down to 11.5v. I am thinking it is a bad alternator, and I am getting fed up so I am going to bit the bullet and buy a new alternator. I will update if that is the cause.
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Old 09-27-2015, 08:19 PM   #3
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If as you say the battery light isn't coming on that has to be fixed before you condemn the alternator. It won't charge without that bulb in the circuit.
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Old 09-27-2015, 09:42 PM   #4
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Any suggestions on getting the bulb to work?
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Old 09-27-2015, 10:06 PM   #5
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Also I checked the voltage of the two wires in the green plug and both were at battery power with key turned to the on position.could the bulb just be bad? It's soldered in and difficult to get to, how would it be replaced?
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Old 09-27-2015, 11:33 PM   #6
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Quote:
Originally Posted by Ceh92 View Post
Also I checked the voltage of the two wires in the green plug and both were at battery power with key turned to the on position.could the bulb just be bad? It's soldered in and difficult to get to, how would it be replaced?
might have to solder if that's what it takes. I've never done it on a subaru, but I did it on my old Saab way back.
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Old 09-28-2015, 07:40 AM   #7
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Does anyone know what bulb? i can eliminate the bulb if I test the wire going to the bulb and it doesn't have power. So if the wire doesn't have power, I should just trace that wire but what am I looking for? Is it for sure this isn't an alt problem and a new alt would fix the light issue?
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Old 09-28-2015, 07:57 AM   #8
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From what you stated you seem to have something going on with the battery warning light circuit that doesn't add up the way it should if it is wired correctly from the factory. You say the light doesn't work yet you also say that there is voltage at the green plug. For that to be true the warning lamp has most likely been bypassed out of the circuit. Power from the ignition switch ties to one side of the warning light and the other end of the light ties to the 'L' lead of the alternator. So the light is in series with the circuit. If the lamp is burned out then the circuit is open and power can't get to the alternator exciter circuit. What is the voltage on that lead while the alternator is running and things are connected up normally? If it is ok you should see about battery voltage on that point. If you have almost no voltage on the lead then there is a problem. If there is a problem I suggest you remove the connector from the alternator and then connect a test light probe between the end of the connector and the clip lead to ground. Testing both of the wires one at a time, they both should turn test light on with the ignition turned ON. If that tests out okay then the alternator most likely is bad. You will also need to find out why the warning light isn't working like it should be.

To test the alternator for a problem and the lamp lead isn't working correctly you could connect up a small light used for the dash lights between power and the L lead to see if the alternator starts working that way. You should see around 14 volts while the engine is running around 1,500 RPM.

Last edited by Cougar4; 09-28-2015 at 08:41 AM.
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Old 09-28-2015, 09:19 AM   #9
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Okay I will check again, I may have mistaken, I checked the wire closest to the front of the car on the green plug not the center wire. So I will check it again and report back what I find out. If I don't have power to the center wire then what should be the next step?
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Old 09-28-2015, 09:35 AM   #10
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Do you have three wires going to the green alternator plug? If so that is a different design than I was thinking of. If you do have a three wire design check the voltage on each of the wires while the alternator is running and let us know your findings. I think all three should have battery voltage on them normally. Also check the output voltage.

A three wire design uses a LED in the cluster for the warning light so that could explain the soldering you mentioned. By grounding the blk/wht lead of the green plug that should turn on the light while the ignition is on if the wiring is okay.

Last edited by Cougar4; 09-28-2015 at 10:10 AM.
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Old 09-28-2015, 10:23 AM   #11
Ceh92
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Default Battery being drained, can't find source.

So it is a 3 wire plug but it only has 2 wires going into it.
http://www.subaruforester.org/vbulle...d-dsc00732.jpg

This is what it looks like
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Old 09-28-2015, 10:41 AM   #12
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Very interesting picture. I'm not sure what to think about this since it has only two out of the three wires. The missing wire normally would go to the ECU to regulate the alternator output. I assume yours internal.

The black/white wire and blue/red wires should have battery voltage on them while the ignition is on and the plug is removed from the alternator. You also should be able to ground the blk/wht wire and have the warning light turn on. In the picture it looks like there is damage to the insulation of the blk/wht wire near the tubing sleeve. Is there a problem there? What is the output voltage of the alternator when running?
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Old 09-28-2015, 10:43 AM   #13
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This is a picture I pulled off the internet as a reference I can post pictures of my actual plug later when I'm off work
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Old 09-28-2015, 10:45 AM   #14
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Okay. You can use those wires shown for reference to yours.
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Old 09-28-2015, 11:03 AM   #15
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Just to make sure I'm doing it right, with the plug plugged in or unplugged do I ground that wire? Am I able to ground the wire with a multimeter?
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Old 09-28-2015, 11:10 AM   #16
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Remove the plug and use a jumper wire to make the ground connection. The meter should never be used to make simple jumper connections. It has a high impedance when in the voltage mode so it won't load the circuit under test.
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Old 09-28-2015, 04:10 PM   #17
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Okay,that makes sense. What do I do if I get the light to come on by grounding that wire? I'm at work and can't try it yet .
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Old 09-29-2015, 12:17 AM   #18
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If the light comes on when you ground the wire it means the light circuit is working correctly. You don't need to do anything to the light. If the light doesn't turn on when you turn on the ignition, with it connected normally, it means something inside the alternator is bad. The alternator grounds the lead when power is on and the engine isn't running. When the alternator is working it supplies aback voltage to that lead which turns of the light, the ground connection goes away unless something goes wrong inside the alternator. Then the warning turns on.
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Old 09-29-2015, 04:16 PM   #19
Ceh92
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Default Battery being drained, can't find source.

So I changed the alternator, the battery light now comes on, but it stays on along with the brake light!? Gah a guy can't catch a break!

Any thoughts on this? I'm done for today I just changed the alt in the pouring down rain.

Alright, I drove it around to see how it would react while monitoring the batt voltage on my cobb. started her up and it was at about 13.5v with the brake light and batt light on. It started dropping and was around the 11.5v range as I was driving (both lights still on). then I parked it and let it idle and watched the cobb. Then the brake and batt light went off and the volts dropped down into the 10 volts range. then the lights came back on it and bumped back up to the 11.5v range and then i revved the engine to about 2k and the lights started to flicker. I drove back home and parked it, then let her idle as I watched, still in the high 11v to low 12v range, then the battery light goes off and I thought well maybe it figured itself out and I'm good to go... WRONG! now the battery light doesn't come on when the key is turned to the "on" position... I feel as though I just wasted my money... and I still am not closer to finding out what is wrong with my car.

Any more help would be appreciated. I should mention that i did the jumper wire on the blk/wht wire and the battery light came on so that is why i resorted to buying a new alternator.

Last edited by Ceh92; 09-29-2015 at 04:57 PM.
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Old 09-30-2015, 12:51 AM   #20
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Well from what you say about the trouble you are now having I think you have one more thing to do. Remove the alternator and take it back to the store. It's bad. You should be able to remove the green connector and the warning light should go out. If you want to prove it again with the ground lead test you can do that but it is most likely okay. If that checks out then a good replacement alternator will fix you up. Hopefully the next one will be better.

Make sure the other lead going to the green connector has battery voltage on it when things are connected normally. Don't ground that lead as that is the battery voltage sense lead for the regulator.
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Old 09-30-2015, 06:15 AM   #21
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Hmmm... I got it from autozone. I do believe you,could it be a wire or something else? Or it's just that common to get a bad alternator?
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Old 09-30-2015, 11:10 AM   #22
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If the test on the blk/wht wire proves out by having the lamp turn on when you ground that lead then there is no doubt about the condition of the alternator, replace it. Having the lamp turn on with the test proves that current is getting to the alternator 'L' lead so the car wiring for that part of the circuit is good. Defective rebuilt alternators are a common problem.
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Old 10-03-2015, 05:08 PM   #23
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So the next time I drove the car (the next day) the battery light and brake light stayed on the entire time. I monitored the battery voltage on my Cobb and it stayed in the mid 13 range the whole time. Is it still the same case when the battery light doesn't turn off when u start the car? Or am I looking for something different? Or is this just a sign of a bad alt?
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Old 10-03-2015, 07:41 PM   #24
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I think you have proven that the alternator has a problem. If you want to verify that then the next time you start the car and see that the warning light is on then shut the engine off and remove the green plug from the alternator. Start the engine again and see if the warning light is turned off now. If the light is off then the wiring is okay (no connection to ground) and the alternator needs to be replaced.
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Old 08-01-2019, 01:58 PM   #25
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I just had this problem with the charge light not showing when first turning the key to “ON”.
I checked voltage at the battery and it was under 12 V at idle. I tried another good alternator from a known vehicle, and the light worked once, but when I started it, the voltage at the battery was still under 12 v, and when I checked the light with the motor off and the key “ON,” the light did not work a second time.
I thought I would check the Voltage output at the alternator post with the car running, and by total accident I saw a small spark being generated between the steel belt cover and the alternator adjustment bracket. I had removed the passenger side bracket mount bolt (that goes thru the grommet) for access to the belt tension bolts, and the cover was just attached at the alternator long bolt, and the cover was suspended at an angle where it just touched the base of the alternator belt tension bracket.
The spark I saw was created by lack of clean grounding surface on the mounting faces of the alternator case. The cover was completing the ground, and the alternator was charging. I moved the cover away and the charging quit. I moved the cover back in contact, and the charging started again.
I needed to use the car, so I removed the rubber grommet from the cover and just clamped that end of the cover down tightly to the steel bracket with a simple bolt, and this grounded the alternator, and everything worked like it was supposed to.
A simple check, would be to connect a ground wire from the negative battery post directly to the case of the alternator with a pair of vice grips.
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