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Old 03-07-2013, 08:10 AM   #1
Zaridar
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Default headlights dimming/flickering, hard starting

04 wrx sedan. When the car is idling and driving the headlights will dim and brighten again noticeably repeatedly when the fan kicks on or sometimes I believe even if either electrical accessories are not turned on... when it's really cold out like this morning 0 degrees it's very hard to start the car... both the battery and alternator are new and this is the second or third alternator I've had on it it's the same results... sometimes even notice interior lights flicker.. the parking light switch is turned on the clock flash is very quickly and very noticeably.. as well as some other interior lights flicker... the daytime running lights have been disabled by on plugging them by the dash passenger side... I also noticed the stock security system is unplugged... I read possibly bad grounds..others say bad battery... but I'm pretty sure those are not the case... somebody please help
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Old 03-07-2013, 08:46 AM   #2
Uncle Scotty
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clean all the grounds and the battery terminals and check the battery cables to see if they are stiff

stiff battery cables are bad juju...means they are corroded inside the insulation....replace them if they are stiff
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Old 03-07-2013, 10:59 AM   #3
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Ok ill double check grounds... how many are on a stock 04 wrx sedan? I think might be missing one ground cable...
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Old 03-07-2013, 11:31 AM   #4
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Is there a way to get new oem cables for older models or should/can we custom fab some?
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Old 03-07-2013, 12:05 PM   #5
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From what you state about the trouble it sounds like the battery isn't getting enough charge from the alternator and it may have excessive ripple voltage due to some bad diodes inside it. The flickering lights is a big indicator the alternator most likely has some bad diodes inside it.

Using a voltmeter check the voltage across the battery while the lights are on and the engine is running around 1,500 RPM. You should see at least 13.5 volts at the battery. Also check the AC voltage across the battery at the same time. If there is more than .1 volt of AC then the alternator has a problem. If the DC voltage is low then move the meter probes and place the common probe on the alternator case and main probe on the alternator output lead. See if the voltage is higher there. If there is more than a .2 volt difference then there is a wire connection problem between the alternator and the battery. The trouble could also be with the ground side.

Note: When checking for AC voltage you need to make sure your digital meter blocks DC voltage. Place the probes across a battery and make sure the voltage reading is zero. Some meters don't block the DC component and that can confuse you if you aren't aware of that. Placing a .5ufd capacitor in series with one of the meter leads will block the DC if your meter doesn't.

Last edited by Cougar4; 03-07-2013 at 12:36 PM.
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Old 03-07-2013, 10:00 PM   #6
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Old 03-07-2013, 10:06 PM   #7
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Old 03-07-2013, 10:10 PM   #8
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I cleaned three grounds, both fenders and intake... didnt have time to get to the one under intercooler... but found the above on my positive cable... what a junk design... cable was loose... put on new terminal... we will see if flickering and hard starting goes away... seems to so far.. although the parking lights on still makes the clock flash violently when headlights are off... ???
thanks for advise for voltages tests... I am now getting 14.2 volts at idle w all accessories on... when ac kicks on it drops for a split second to 12.8 v then right back up... need to do ac v test do these reading seem normal?
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Old 03-07-2013, 10:20 PM   #9
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Quote:
Originally Posted by Zaridar View Post
I cleaned three grounds, both fenders and intake... didnt have time to get to the one under intercooler... but found the above on my positive cable... what a junk design... cable was loose... put on new terminal... we will see if flickering and hard starting goes away... seems to so far.. although the parking lights on still makes the clock flash violently when headlights are off... ???
thanks for advise for voltages tests... I am now getting 14.2 volts at idle w all accessories on... when ac kicks on it drops for a split second to 12.8 v then right back up... need to do ac v test do these reading seem normal?


sounds like something back powering the system somewhere

whatever wiring you---or somebody else...has done may not be quite right
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Old 03-07-2013, 11:56 PM   #10
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The voltages look pretty good but the drop to 12.8 volts may mean the battery is slightly weak. You can get a load test done on it if you have some doubts on it. I suspect you are going to find excessive AC voltage when you test for it since you say the lights are still flickering. The bad battery terminal connection may have been causing the battery to not get a full charge from the alternator. Dirty battery connections are a very common issue and are so simple to fix.
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Old 03-08-2013, 12:00 AM   #11
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battery is new and has been tested...I work at AutoZone and am pretty mechanically / electrically inclined... but this one is just killing me... this is an STi Alternator...
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Old 03-08-2013, 07:03 AM   #12
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Quote:
Originally Posted by Uncle Scotty View Post


sounds like something back powering the system somewhere

whatever wiring you---or somebody else...has done may not be quite right
This.. whats been done to the car electrical wise..?
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Old 03-08-2013, 11:49 AM   #13
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The only thing I know of that can cause the dash lights to flicker rapidly is due to bad diodes inside the alternator.
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Old 03-08-2013, 01:51 PM   #14
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Quote:
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This.. whats been done to the car electrical wise..?
I put in a boost gauge that is all I have done... the guy before me put in a aftermarket dvd player... and also did the non daytime running light mod... the DVD player has a toggle switch left side of the dash so you can watch DVD's while rolling.. that's all that has been done to it electronically as far as I know... I put in HID's .. then put in a heavy duty wiring harness w/relay.. but then removed them.. so everything is back to stock..
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Old 03-08-2013, 02:15 PM   #15
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Old 03-08-2013, 02:16 PM   #16
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You had a bad battery connection so your new battery is not fully charged. Charge the battery and then see if the flickering goes away.
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Old 03-08-2013, 02:22 PM   #17
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with lights on only at idle.. 14.18v at alt...14.06 at batt... AC test came up with 30 volts.. I'm guessing I need to try it with a resistor
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Old 03-08-2013, 02:29 PM   #18
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with all accessories on I'm losin about .3 to.4 volts between alternator and battery and when the AC fan kicks on... voltage still drops to about 12.7 to 12 .8.... I haven't driven at night yet but I need to check still if the lights flicker.. however the clock flashing is still very prevalent.... I don't think the interior lights other than that flash at all
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Old 03-08-2013, 02:32 PM   #19
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AC 30 volts? Your alternator diode pack is fried.
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Old 03-08-2013, 06:49 PM   #20
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ive never used a multimeter to do AC volts... it was on 200 scale and was reading 30.. i think i need a resistor like stated above.. its a cheap Multimeter
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Old 03-08-2013, 10:40 PM   #21
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Set the meter to read AC volts instead of DC. It sounds like your meter doesn't block DC voltage while in the AC function. To see if that is the case just take any battery and see if you get a reading while in the AC mode. If you do then you need to put a capacitor, not a resistor, in series with one of the probe leads or get a meter that does block DC. If you need to get a capacitor get a .5 microfarad @200VDC, or something close to that area.

If your meter does block DC then you really need to replace the alternator since 30 volts of ripple is really bad. I suspect though your meter is allowing the DC to pass through also.
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Old 03-09-2013, 02:42 AM   #22
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hmm why would it be 30 vdc?
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Old 03-09-2013, 10:06 AM   #23
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When the engine isn't running, are the headlights flickering?
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Old 03-09-2013, 11:43 AM   #24
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Quote:
Originally Posted by Zaridar View Post
hmm why would it be 30 vdc?
It can't be 30 volts DC. I assume you are asking if it could be 30 volts AC and that is possible but it would be very bad for the battery and other things if that was the case. The results you got though seems to indicate good news possibly as 30 volts AC would be the correct reading for a meter set to read AC volts, doesn't block DC, and there is around 13 to 14 volts of DC across the probes. Any added AC voltage would add to that reading if there is some. As an experiment in science and technology and your own personal knowledge, you might try adding the capacitor to the probe and then check the AC voltage. You will have to use a lower scale to make the reading since the DC will now be blocked from the meter. See if the voltage is less than.1 volt AC while the engine is running.

Note: CRAZYHAWK brought up a good point on this issue. If the light flickering is due to the alternator then it won't happen when the engine is off and the other accessories are on.

Last edited by Cougar4; 03-09-2013 at 11:48 AM.
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Old 03-09-2013, 01:39 PM   #25
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ok got ya.. the clock flickers regardless of engine running or not'
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