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Old 04-20-2008, 02:52 PM   #1
WRBLueGD2
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Angry My battery dies if the car idles with the E-Brake on

Any ideas what is causing this? As far as electrical goes, I didn't really do much.
  • Boost and EGT gauge
  • Standard Pioneer head unit
  • Hooked up Hella Supertones without the resistor box
  • Swapped my gauge cluster bulbs to LEDs
  • Disconnected my seat beat chiming alarm
  • Disabled day time running lights
  • Performed the fog light stand alone trick
All of this was AFTER this issue sprout however. I've been having this issue for about a year now and it's bugging the hell out of me. That and when the ABS light comes on and clicks off, mine will stay on some time WITH the brake light. Any idea what the hell is wrong?

Sometimes I will turn the key, all the status lights come on and go off. The ABS sometimes stays on as well as the BRAKE light (even with the brake handle down) and stays on the whole time. If I pull in somewhere and run inside while the car idles with the E-Brake on (No lights, radio normal) and after about 5 -10 minutes that car will start to idle very oddly. If I push the gas, the car cuts out or dies. Then I have to jump start it to get it to kick on.
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Last edited by WRBLueGD2; 04-20-2008 at 02:57 PM.
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Old 04-20-2008, 11:23 PM   #2
Cougar4
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I suggest you have the alternator checked to see if it has the proper output. Also check to see if there is any AC at the output, indicating bad diodes.

Clean the battery connections using a battery cleaning brush. Clean and check the grounding to the chassis.
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Old 04-21-2008, 08:55 AM   #3
WRBLueGD2
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Alternator was replaced, clean the battery terminals with water and baking soda and reconnected them with vaseline. I bought a grounding kit, maybe that will help, but I'm going to go in through the console and check any wires I find.
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Old 04-21-2008, 12:19 PM   #4
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I see you cleaned the battery terminals but did you clean the contact surfaces of the battery posts and cables using a battery post cleaning brush? This is important since it removes any surface layer on the connections that can cause trouble. I assume you didn't put any vaseline on the contact areas as this acts as a insulator.

If the E-brake light is coming on while the ignition is turned OFF then there is a back feed coming from somewhere. If this is so you can pull fuses to help you locate the source of trouble. My first check would be to remove the small wire connector on the alternator to see if that is where the trouble is coming from. I have seen that happen to others in the past.
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Old 05-05-2008, 08:59 AM   #5
WRBLueGD2
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So i got my Access Port finally and I've been cruising around with it running some live displays for me. I used the volt meter to check my battery. During normal driving and sitting at a light, it sits around 13.8 - 13.4 volts. If I stop anywhere and just let the car sit, it stays in the values. As soon as I pull the E-Brake my output drops to 12.0 then to about 11 flat. This can't be normal.

Just parked, no E-brake, A/C on full blast it's still getting 13.2 to 13.5 consistently. Apply the brake and it drops immediately to 11.5ish and then sits around 11.1 to 11.

What's my issue? Battery? Alternator was replaced about 1000 miles ago.
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Old 05-05-2008, 09:52 AM   #6
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It sounds like there is a real high load being put on the electrical system when the E-brake is on. It would be good to know what the voltage is directly at the battery when the brake is on just in case there is a problem with the circuit to the E-brake.

Do you know what shape the battery is in? If not, I suggest you get a load test done on it. The trouble may also be with the brake causing the alternator charging circuit to fail. There may be a bad blocking diode. I will have to look at a diagram to see about that.
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Old 05-05-2008, 10:25 AM   #7
WRBLueGD2
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Battery is original

Time for an Optima?
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Old 05-05-2008, 03:25 PM   #8
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I would have the battery tested before doing anything with it. It may be ok but just needs charging. As far as Optima batteries go, I don't see why spending so much on a battery makes a real difference for most folks that get them. You can purchase two very good Die Hard batteries for the price of one Optima. I have a Die Hard battery that is over 12 years old in my truck. That is just my opinion though. You could purchase a nice voltmeter with the money saved on the battery, if you don't have one.

BTW, what is the year and model of your car?

Last edited by Cougar4; 05-05-2008 at 03:31 PM.
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Old 05-05-2008, 04:32 PM   #9
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I looked at some data for a '04 WRX and it shows that a diode located in the dash combination meter isolates the E-brake and alternator circuits. The data shows that a blk/wht wire going to the alternator has a diode in the circuit to stop voltage backfeeding to the E-brake. If you see that wire on the alternator, disconnect it and then see if the voltage drops when the brake handle is up.
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Old 05-05-2008, 05:14 PM   #10
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did u buy used? could have been prev turbo timer
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Old 05-06-2008, 01:31 PM   #11
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Check your battery connection (+/-) make sure - is grounded tight to the chasis.
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Old 05-07-2008, 10:20 AM   #12
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Quote:
Originally Posted by Cougar4 View Post
I looked at some data for a '04 WRX and it shows that a diode located in the dash combination meter isolates the E-brake and alternator circuits. The data shows that a blk/wht wire going to the alternator has a diode in the circuit to stop voltage backfeeding to the E-brake. If you see that wire on the alternator, disconnect it and then see if the voltage drops when the brake handle is up.
Wow, thanks for that info. I would've never found it otherwise.
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Old 05-17-2008, 07:23 PM   #13
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Quote:
Originally Posted by WRBLueGD2 View Post
Wow, thanks for that info. I would've never found it otherwise.
This is what I came up with. This is the only thing that had a black and white wire running to the alternator.

I pulled off the entire unit as pictured and started the car. It idled at around 12.0 - 12.4 volts. I dropped the E-Brake and got no change whatsoever.

I popped it back on and started the car again. It idled again around 12.0 - 12.4. I dropped the E-Brake and it instantly spiked to 13.1 then 13.6 then 14.0

What's the deal here? Do i have to pop that white wire out somehow? I don't think my car should only run at 12.5 volts though... This was all measured at idle though.
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Old 05-18-2008, 10:29 AM   #14
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The measurements you took seem to verify that there is a problem with the blocking diode in the brake light warning indicator. When you pulled the brake handle it closes the brake switch and makes a ground connection. This will ground the blk/wht wire going to the alternator, if the blocking diode is shorted, through another diode in the ciricuit. To verify that another way you could measure the voltage on the blk/wht wire going to the alternator and everything connected normally while the car is idling. First measure the voltage on the wire with the E-brake off and then with the E-brake on. I suspect the voltage will drop to around .7 volts with the brake on. This would mean the blocking diode is bad. You will most likely have to replace the warning light module unless you can get to the inside of it and replace the bad diode.
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Old 05-19-2008, 09:10 AM   #15
WRBLueGD2
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Test it by taking that clip back off? Test the pin with the Brake on and off and it should change? Or hows the best way to test it? And how would I change the warning light indicator and/or the diode?
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Old 05-19-2008, 12:49 PM   #16
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Check the voltage on the blk/wht wire, on the back side of the alternator, using a voltmeter. Leave everything hooked up as it should be. If you can't place a meter probe on the back side of the connector to make connection you will have to pierce the insulation of the wire. You should cover the hole afterwards with some silicone if you do that. Start the car and leave the E-brake off. Measure the voltage on the blk/wht alternator lead. Then apply the E-brake and measure the voltage again. Write down the voltages you read for both measurements and let me know what they are. The voltages readings are of course taken with reference to a good ground point, like the alternator case.

The data I looked at seems to indicate that the brake warning light is a module with more than just a light in it. If that proves to be bad you will need to replace the small module.
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Old 05-21-2008, 12:31 PM   #17
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What kind of Pioneer Unit? Standard meaning cd player only?
What year car/model?
What was the result of Cougars test recommendation?
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Old 05-21-2008, 05:28 PM   #18
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Ok, I jacked a volt meter from work (PC Tech, lol).

Car was at idle sitting in my driveway. No lights, door open, radio on average to low volume. I used as a ground the alternator case, ground terminal on battery, and car frame. I used all three ground points for ALL FOUR readouts to ensure accuracy.

E-Brake OFF:

  • 14.1v at the battery terminals
  • 13.45v at the wire where it connects to the alternator

E-Brake ON:

  • 12.5v at the battery terminals
  • 0.65v at the wire where it connects to the alternator

So the results show that when the ground is made from my E-Brake, it kills the voltage! What now?
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Old 05-22-2008, 01:37 AM   #19
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Good job on the voltage checks. From looking at the results it appears I may have been correct about the shorted diode in the brake warning light section of the combination meter. I suggest you replace it and then see what the voltages are when the brake is ON. You will notice that the voltage reading at the battery goes down to the battery voltage when the brake is ON, the alternator isn't charging at all.

One thing you could do in order to use the brake until this is repaired is to disconnect the wire going the the E-brake. This should break the ground path and keep the circuit isolated from ground. You can prove it by rechecking the battery and wire voltages after removing the wire to the E-brake. The charging voltage should stay up when the brake is ON. Of course there will be no warning light to show the brake is ON if you do that, so you need to keep that in mind if you do this. You can also just not use the E-brake.

Another alternative I just though of is you could install a diode in series with the blk/wht wire going to the alternator to block the current path. This will be a small modification which I don't normally recommend doing but it would probably save you a lot of money. The diode would have to be placed so the anode (the arrow head) points towards the alternator. I would guess a 1N4001 diode would work ok. This is just a general purpose diode and can be purchased at any electronic parts store.
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Old 05-22-2008, 11:12 AM   #20
Cougar4
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After thinking about this problem and reading your original post again I think it would be wise to do one more test to verify that the blocking diode is bad in the combination meter. You will need the digital voltmeter to perform the test and set to the diode test function. I would like to verify that the diode is shorted. Here are the steps you need to do to make the test:

1. Ignition switch is OFF
2. Remove the connector at the alternator that has the blk/wht wire going to it.
3. With the meter set to the diode testing function, place the red lead of the meter on the connection to the blk/wht wire. Place the meter common lead on the alternator case ground. If the diode is bad you should see a reading of about .70 on the meter. If the diode is really ok then the reading will show 'OL' or perhaps 1.5.

Last edited by Cougar4; 05-22-2008 at 11:24 AM.
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Old 05-26-2008, 09:00 AM   #21
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Haven't gotten to check it yet. What if it's the same issue? Change the Diode? Am I going to have to have the dealer do this? And is it going to be an expensive fix ya think?
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Old 05-26-2008, 11:36 AM   #22
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I would like you to follow the instructions in post #20 when you get a chance just to make sure that the alternator isn't causing the trouble somehow.

I suspect you will verify that the trouble is with the diode in the combination meter and if so you would most likely have to replace the whole meter assembly. I'm sure it would be expensive. If I was working on this I would try getting into the meter and replace the diode itself. This would not be a job that all would be comfortable in doing but isn't real complicated either. The simple solution to this would be to follow the instuctions in the last paragraph of post #19.
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Old 06-01-2008, 07:57 PM   #23
WRBLueGD2
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Thumbs down

Results are in. I used 2 digital volt meters. I test the battery each time with each volt meter on each test.

With the E-Brake off, I consistently got 12.4 volts at the battery, 11.9 volts at the wire, while unplugged from the alternator.

With the E-Brake on, I consistently got 12.3 volts at the battery, 0.9 volts at the wire, while unplugged from the alternator.


So, the diode is bad? And idea where I can read up on how to replace it? If not, what do I tell the repair center at Subaru?
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Old 06-01-2008, 11:18 PM   #24
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Question. Do you know how to set up the meter to test in the diode test function?

The last results you gave isn't what I wanted you to do exactly. In order to prove without any doubt that the blocking diode is bad in the combination meter I wanted you to do a diode test and that is why I ask you that question. It is easy to set up if you don't know how. It is like checking for resistance but the meter displays differently. If you need help with it I can tell you how to do it.

Last edited by Cougar4; 06-01-2008 at 11:45 PM.
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Old 06-02-2008, 07:56 AM   #25
WRBLueGD2
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yea, I dont kno how to do that
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