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Old 10-31-2011, 08:18 PM   #1
fourage20
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Default brake and battery light on.

so my battery light and brake light have been on since febuary. i checked the alternator and battery and are in good working order. i also checked all the grounds and they are all hooked up and clean. the car does have brake fluid too. i also checked the connection on the ebrake itself and is hooked up. both these lights came on at the same time and the car has never left me stranded. can someone PLEASE tell me what the hell is going on with it? lol
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Old 10-31-2011, 09:25 PM   #2
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How exactly did you check the alternator? It may have bad diodes, which will allow it to still charge but with reduced output and excessive AC ripple. Checking the system voltage with a basic DC voltmeter will not reveal this type of problem.
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Old 10-31-2011, 10:20 PM   #3
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actually i changed the alternator. lol. when the problem started, i had a sti alternator in the car. so i changed the alternator to my stock wrx one and a different battery, and the problem continued. i drove like that till i did an engine swap then went back to the sti alternator. still have the same problem.
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Old 11-01-2011, 07:08 AM   #4
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Try disconnecting the plug on the rear side of the alternator and then start up the car to see if the warning lights are still on. If they are then there may be a problem within the cluster.
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Old 11-01-2011, 01:13 PM   #5
fourage20
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Ok I disconnected the connector on top of the alternator with the red cover on it. The battery light went away and the Ebrake was dim but still on. Both lights came back when I reconnected the red connector.
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Old 11-01-2011, 02:36 PM   #6
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Take alternator to a auto parts store they have a machine to actually test it. Would check that before anything,
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Old 11-01-2011, 04:07 PM   #7
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Quote:
Originally Posted by fourage20 View Post
Ok I disconnected the connector on top of the alternator with the red cover on it. The battery light went away and the Ebrake was dim but still on. Both lights came back when I reconnected the red connector.
It sounds like you disconnected the main output lead of the alternator instead of the wires going to the back side of the alternator which are the ones I wanted you to disconnect. See what happens by doing that anyways. I suspect that even if you do that the results will be the same but it may change some things possibly. Check to see what the voltage is on the field lead of the alternator while the alternator is running and wires connected normally. It should be close to battery voltage. If it is close to ground then the alternator may be at fault. The field lead wire color may be white/red.

There could be another thing causing the fault if the warning lights stay on when the field lead is removed from the back side of the alternator while the ignition is on and the engine is off so you need to check that. If they stay on then there is a ground fault on the field wire, possibly from a bad diode in the cluster.

Normally the field lead on the back side of the alternator should be close to ground potential when the key is turned on and the engine isn't running. Power from the ignition switch ties to the warning lights and then to the alternator field lead which should be near ground potential and that turns on the warning lights for a test. When the engine is started, the alternator uses the current going through the field circuit to energize the field of the alternator and start the charging action. It also builds up a backfeed voltage on the field lead which turns off the warning lights. The lead isn't at ground potential anymore, until the alternator stops turning or has a problem.

Last edited by Cougar4; 11-01-2011 at 04:33 PM.
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Old 11-01-2011, 05:42 PM   #8
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If the same problem exists with 2 different alternators and 2 different batteries then it's probably not the alternator. It may be a bad alternator wire or bad connection on the car.
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Old 11-01-2011, 06:46 PM   #9
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Ok I disconnected the plug on the back of the alternator and the same thing happened. The battery light went away but the brake light stays on but dimmer. When I pull the Ebrake up the light gets brighter.
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Old 11-01-2011, 06:57 PM   #10
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Ok. Since the battery light went out that means the path to ground for the battery warning light is through the alternator, like it should be. Since the brake light is still staying on but dim it may mean there is something going on inside the cluster that shouldn't be. I still suspect there may be something wrong inside the alternator. It would be go to know what the voltage is on the field lead with things connected normally and the engine running. If the voltage on that lead is low then I think the alternator has a problem.

Edit:
I just thought of another thing. With the rear connector of the alternator removed and the ignition ON, check the voltage on the field wire going to the plug using ground as a reference. See if the voltage is less than a few volts. If so that may prove there is something wrong inside the cluster also.

Last edited by Cougar4; 11-01-2011 at 07:21 PM.
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Old 11-01-2011, 06:58 PM   #11
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Quote:
Originally Posted by jgardiner View Post
If the same problem exists with 2 different alternators and 2 different batteries then it's probably not the alternator. It may be a bad alternator wire or bad connection on the car.
I agree, it would seem strange to have two alternators with the same fault of this type. The fact though that removing the battery lead to the alternator made the lights go out seems to indicate that there is a problem with the alternator. The battery certainly cannot cause this kind of trouble.
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Old 11-01-2011, 10:40 PM   #12
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Ok so I feel like a dick. It was a fuse for the alternator. It was a 10 amp fuse that was blown. But I still have the Ebrake light on. It gets dim with the e brake is down and gets brighter when I pull the Ebrake up. Any ideas?
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Old 11-02-2011, 12:35 AM   #13
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Well don't feel bad, things like that happen to a lot of folks. I am a bit mistified as to how the alternator was working with the blown fuse. Do you know what the fuse number is of the fuse that you replaced? It must have to do with something inside the cluster. It may be providing power to a part of the circuit I am not aware of right now and was providing the battery light a ground somehow.

As far as the brake light, check the alternator output and see if there is any AC voltage coming from it across the battery. There should be less then .1 volt AC across the battery with the engine running. If that is ok then I would have to say there is a bad diode inside the cluster than is allowing the brake light to be on. A diode may have some leakage in the reverse direction which is allowing the light to glow slightly.
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Old 11-03-2011, 12:10 AM   #14
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ill check which fuse it was in the morning. i fixed the brake light too. the wire that goes to the e brake from my dccd was causing it to stay lit. i need to put a diode or something on it i think. im just glad those dumb lights are off.
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Old 11-21-2011, 01:26 AM   #15
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strange i'm having a problem like this its would flicker for a few weeks and turns off some time. now it seems to stay on now but will turn or flicker at times i'll be checking this stuff tomorrow i tired to load up the system with lights brakes and A/C
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Old 02-16-2018, 06:58 PM   #16
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Default Same problems

I disconnected the alternator plug on the back and my brake light and battery light went out I disconnected the positive terminal the car died I reconnected the plug on the back of the alternator the lights came back the battery light and brake light indicator you mentioned a cluster could be burnt out where is the cluster located = I I disconnected the plug on the back of the alternator and the same thing happened. The battery light went away but the brake light stays on but dimmer. When I pull the Ebrake up the light gets brighter.[/quote]
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Old 02-16-2018, 07:01 PM   #17
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Default Had the alternator tested it is a new one from advanced

The salty roads here in New England don't do any Goods for the wires could the connection on the back of the alternator be bad ? My low beams were burning out
=Cougar4;35526343]Well don't feel bad, things like that happen to a lot of folks. I am a bit mistified as to how the alternator was working with the blown fuse. Do you know what the fuse number is of the fuse that you replaced? It must have to do with something inside the cluster. It may be providing power to a part of the circuit I am not aware of right now and was providing the battery light a ground somehow.

As far as the brake light, check the alternator output and see if there is any AC voltage coming from it across the battery. There should be less then .1 volt AC across the battery with the engine running. If that is ok then I would have to say there is a bad diode inside the cluster than is allowing the brake light to be on. A diode may have some leakage in the reverse direction which is allowing the light to glow slightly.[/quote]
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Old 02-16-2018, 07:34 PM   #18
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7-year-bump not approved.
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