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Old 06-05-2008, 12:18 AM   #1
Sir Punk
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Default brake and battery lights on

I already read the previous threads and done a bunch of tests but I get a weird behavior. my battery and brake lights go on but only when I don't use the clutch for some time. It's been happening when I am on the highway, maybe after 20 minutes, today after 5 minutes of 5th gear, then as soon as I push the clutch the lights go off and when I release they come on again after a few seconds, this doesn't happen in 4th gear. I got this the first time 2 weeks ago. Last sunday I drove for 30 minutes in the city with no problems. all electrical things work just fine.

I checked the battery, the alternator, brake fluid is closer to MAX than it is to MIN. Check the grounds. DC at idle was 14.2. One thing was weird, that I am not sure if it is related to it. Before the problem started I found a black screw on the driver mat and I couldn't figure out where it came from. I also checked under the dashboard and everything seems fine, the wiring harness is in place and nothing pinches on the clutch. the fuse box is fine. am I missing something? the alternator is re-manufactured and this is a 99 impreza

any ideas?
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Old 06-05-2008, 10:35 AM   #2
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This is a strange one alright. Usually when those lights come on it is an indication that the alternator is having a problem. Even though your charging voltage appears to be ok at idle there may be a problem happening inside the alternator at high speed. Before replacing the alternator I recommend you check the grounding between the engine and chassis along with the battery and chassis grounding, just to make sure something isn't wrong there. If you don't have any good results cleaning the ground connections then I recommend you try a different alternator.
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Old 06-05-2008, 10:41 AM   #3
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ok, I just measured the battery voltage under load. I turned on all lights, fog lights, heat, fan at 4, cruise control. it went down to 13.8 then back up at steady 14.2 or so. the battery was at 12.5. the thing is that as soon as I hit the clutch it goes away even if I'm at high speed. I drifted for a minute or so and the lights stayed off. I checked the grounding and cleaned the one on the engine block, I guess I'll do the same with the ones on the chassis.
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Old 06-05-2008, 10:43 AM   #4
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voltage drop test!! always the place to start with potential alternator problems, measure voltage from battery + terminal to alternator post, and voltage from alternator case to battery - terminal do it with all loads on in the car and engine revving at about 2K rpms.

voltage should be less than ~.3
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Old 06-05-2008, 10:49 AM   #5
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Quote:
Originally Posted by ProdriveDreams View Post
voltage drop test!! always the place to start with potential alternator problems, measure voltage from battery + terminal to alternator post, and voltage from alternator case to battery - terminal do it with all loads on in the car and engine revving at about 2K rpms.

voltage should be less than ~.3
ok I haven't tried that specifically. I'll do that ASA I get home.
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Old 06-05-2008, 11:45 AM   #6
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An alternator may work fine at low RPM but not at high RPM.
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Old 06-05-2008, 12:19 PM   #7
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There may be some bad diodes in the alternator, if so the voltage will read normal on a meter. This type of problem can only be diagnosed accurately on a shop scope.
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Old 06-05-2008, 01:15 PM   #8
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Quote:
Originally Posted by Cougar4 View Post
An alternator may work fine at low RPM but not at high RPM.

wouldn't that option be out since it doesn't happen in any other gear rather than 5th?

someone suggested the brake fluid that should be close to max.
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Old 06-05-2008, 03:41 PM   #9
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Quote:
Originally Posted by Sir Punk View Post
someone suggested the brake fluid that should be close to max.
this should not trigger the charging light also if that was the case
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Old 06-05-2008, 03:55 PM   #10
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Quote:
Originally Posted by Sir Punk View Post
wouldn't that option be out since it doesn't happen in any other gear rather than 5th?

someone suggested the brake fluid that should be close to max.
I can't explain why the different gears are effecting the lights. It could be just a coincedence since you are most likely taking your foot off the accelerator also when you shift and it is really related to the alternator RPM. I suspect the real trouble is within the alternator.
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Old 06-05-2008, 08:27 PM   #11
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ok so, I finally figured it out. the alternator works fine at low RPMs, but when the car stays steady around 3k then it doesn't work anymore and the battery starts going down around 12 and it went to 11.5. so the clutch had nothing to do with it, but now it all makes sense because in the city the rpms fluctuate a lot. so now I need an advise on which alternator I should get.
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Old 06-05-2008, 08:42 PM   #12
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I usually just get the autozone duralast ones as they come with a lifetime warranty.
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Old 06-05-2008, 08:53 PM   #13
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is it possible that the alternator can be fixed? because it can cost around $150
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Old 06-05-2008, 08:57 PM   #14
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Quote:
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is it possible that the alternator can be fixed? because it can cost around $150
yes but usually thatll cost you almost as much as a new one.
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Old 06-05-2008, 10:02 PM   #15
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I've seen alternators that fail when hot and work again when cold multiple times. They are a BITCH to diagnose and it sounds like your problem may be similar.
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Old 06-05-2008, 10:10 PM   #16
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I just had another thought. could it be the belt?
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Old 06-05-2008, 10:32 PM   #17
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I don't think so. Make sure it is snug though and not over tight. To me, having those two warning lights come on means internal trouble with the alternator.
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Old 06-05-2008, 11:05 PM   #18
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thanks guys. I'll be looking for an alternator with a lifetime warranty then. I don't run that many things, I just have a pioneer 6-cd changer with pioneer speakers but no sub. so a 75amp alternator should be ok.
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Old 06-06-2008, 12:21 AM   #19
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pretty sure baja's have 90 amp alternators... go to someplace like autozone see if they have both in stock and ask to compare them the difference to look for would be the harness that connects to it the plug might be different.... if its the same your good to go.
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