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Old 05-14-2008, 02:54 AM   #1
jojofett
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Default STi gauge light problem

Hi everyone. So I have a 2005 Sti. Sometimes when I drive around or when I turn on my car, 3 warning lights flicker, or stay on for a bit. The lights are the "Brake" "Battery" and "Rear Diff" light. I dont know why they do this but its a bit bothersome. I've included a link to a video on youtube. Someone please help!!!!

http://www.youtube.com/watch?v=I3K3GActtZs
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Old 05-14-2008, 09:17 AM   #2
Mulder
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You may have a slipping alternator/PS belt or the alternator may be failing. The belt is easy enough to check, a voltmeter across the battery should indicate how well the alternator is charging although it can have bad diodes and still indicate normal voltage on a meter.
If the belt is ok and the voltage is in the normal range (13.5-14.5V with the engine running), a shop can do a more thorough diagnosis on the electrical system.
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Old 05-15-2008, 05:17 AM   #3
jojofett
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Im getting a volt reading of just over 15. So does that mean I should take it to a shop to have it diagnosed?
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Old 05-15-2008, 09:15 AM   #4
ProdriveDreams
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unless your battery was quite low because you left your lights on/ played the stereo for a good while with the car off, etc. then yes i would have htat checked out. You wouldnt happen to have corrosion on your battery would you? sometimes that can lead to trouble with voltage sensing then overworking the alternator.

Do a voltage drop test to the alternator post with the car running. voltage from alternator post to + battery terminal should be no more than .3 volts or so also check from alternator casing to - battery terminal.
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Old 05-16-2008, 01:41 AM   #5
jojofett
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I'll have to do that voltage drop test. The battery is new and the posts are clean of any corrosion. I'll update you once I've done it.

By the way, thanks for helping me out. I really appreciate it.
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Old 05-16-2008, 05:39 AM   #6
Cougar4
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Those lights you mention are probably in the alternator field circuit so if the alternator is having trouble the lights turn on. This is designed so the dash lights can be tested when you turn the key to ON. The fact that you are also going over 15 volts isn't good either. It looks like you are going to need to replace the alternator.
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Old 05-16-2008, 10:00 AM   #7
jojofett
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Ouch. Ok, heres something. I bought the car used so the battery is not factory. The battery is an AC Delco battery. Should I be concerned? Are there any specific ratings of the battery that should be required of the STi?
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Old 05-16-2008, 02:00 PM   #8
Cougar4
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The only real concern about a battery normally in any car is the capacity it has to power the cars accessories and have the cold cranking amps to drive the starter motor, particularly on those real cold mornings. If the battery you have meets the minimum specs for your model then you are good to go. Even if the current battery was undersized for the car it wouldn't cause the kind of problem you are having. The Delco battery is a good one and if it has at least a 60 month warranty it should last a good while. By keeping the battery connections clean and the alternator running well it will help extend the battery life. One thing that hurts a battery is over charging it and while 15 volts isn't real bad it is at the top end of the safe charging range. The regulator inside the alternator keeps the voltage in a safe range. There does seem to be a problem with your alternator since the warning lights are turning on, there may be some bad diodes in it. To verify it, you may want to have a shop check the alternator out before replacing it. It may not pass the full output test due to some bad diodes.

The test procedure given in post #4 is a good one to check and see if there is a problem with the connections between the battery and the alternator output. It should be done with a good load on the system. The ground wiring can also be checked in the same way. If you have a shop test things out they should do those tests for you also.

Last edited by Cougar4; 05-16-2008 at 02:07 PM.
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Old 05-16-2008, 09:16 PM   #9
deuce106
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i had that same thing before. i bought a used alternator and replaced it. never happened since.
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Old 05-16-2008, 10:39 PM   #10
ProdriveDreams
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If you do buy an alternator to replace it with, I highly recommend Autozone duralast alternators, I'm pretty sure they are refurbished OEM ones... Regardless they come with a lifetime warranty.

I bought one when my alternator died in my legacy while in the middle of no where maine, luckily I have a yellow top so i had plenty of drive time, and i picked one up. The problem is my charging system has way to much resistance in it, but the wires are a bitch to get too, so i just keep a ratchet and a 10+12mm socket in the car. It dies every 4-6 months or so and i just role to the closest autozone and start again... hahahah oh the things i do to my beater i'd NEVER consider in the WRX.
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Old 05-20-2008, 01:05 AM   #11
jojofett
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Default

Thanks for the diagnosis guys. I tried to go to Autozone for a new alternator but they didnt have one in stock. Anywhere. So the guy suggested I go to this Ma and Pop shop who rebuilds alternators. I took it to them and they did it for $145. She said it was cuz the parts were expensive for this alternator. That was fine by me. They got it done in 5 hours. When I got it, I thought I was looking at a new alternator. Its pretty cool now cuz the core is red like the STi manifold. So it kinda matches. In any case I'm happy now cuz the warning lights are now off! THANKS AGAIN!!!
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Old 05-20-2008, 03:35 AM   #12
Cougar4
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You are welcome for the help Jojofett. Glad you got it fixed and thanks for the feedback.
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