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Old 10-21-2009, 04:25 PM
 
Location: Kansas
3,855 posts, read 13,223,598 times
Reputation: 1734

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Issue just what the title says. When idling the dash lights flicker as well as the headlights.

Idle is a little rough but not real bad.

Alternator: good
Battery: new
Voltage indicated: 14.xV

If it matters it's a 2002 Chevrolet Blazer 2wd 4dr with 4.3L V6, automatic tranny.
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Old 10-21-2009, 04:41 PM
 
Location: Eastern Washington
17,106 posts, read 56,712,890 times
Reputation: 18365
No idea if this is your problem or not, but my Scirocco was doing that awhile back, it turns out that the voltage regulator, held to the alternator by 2 screws, was loose, one screw had fallen out and the other one was loose.

No, I wasn't smart enough to find the problem at this stage, I kept driving it with the flickering lights till the 2nd screw fell out as well, which of course made the alternator go to max output...

fortunately I was close to home, was able to figure out what happened and unplug the alternator entirely, drive home on just the battery...

So, if your alternator has an "onboard" regulator, take a look at the regulator's mounting screws...

One thing is certain, if you don't find the problem at this stage, Mr. Murphy will make it more obvious for you, normally at a rather inconvenient time..
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Old 10-21-2009, 05:04 PM
 
Location: Lehigh Acres
1,777 posts, read 4,835,741 times
Reputation: 891
normal operating condition
clean your throttle body with some carb cleaner and an old toothbrush
you can upgrade to a larger CCA battery and a higher output alternator, but the harness can only handle so much power anyways
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Old 10-21-2009, 09:14 PM
 
Location: Memphis, Tn ~ U.S.A.
2,352 posts, read 5,341,649 times
Reputation: 2181
Maybe your dash light bulb is going out
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Old 10-21-2009, 09:51 PM
 
Location: Tulsa, OK
5,987 posts, read 11,629,112 times
Reputation: 36729
Sounds like it's idling slow enough that the alt doesn't know if it wants to put out or not. If you pick up engine speed about 100 RPM does the problem stop?
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Old 10-21-2009, 10:44 PM
 
11,548 posts, read 52,903,008 times
Reputation: 16318
The flickering is a result of voltage surges.

This can be due to many possible factors, including a bad voltage regulator, an alternator that's not in good condition (possible bad diode, bad rotor/stator, poor internal connections), poor/high resistant charging system connections, poor/high resistant grounds, and also the idle surging is enough to cycle the alternator in/out of the charging system.

System voltage may not capture the fault. You need to check the wiring system wiring and connections for voltage drops (high resistant connections) with the voltmeter, or use a o'scope to capture the alternator voltage fluctuations that a voltmeter won't reveal.

If you aren't familiar with these types of tests, or don't have the equipment, then you'll need to take the car to an automotive electrical shop ... one that actually can test for the faults, as opposed to many shops that will simply start replacing parts.
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Old 10-22-2009, 07:41 AM
 
Location: Earth
4,237 posts, read 24,688,387 times
Reputation: 2274
Another vote for a bad vr. Had one go bad on an alternator once....yes the alternator worked but the volts would increase and decrease with engine rpm speed....as a result the lights would get brighter and dimmer.
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Old 10-22-2009, 08:30 AM
 
Location: Kansas
3,855 posts, read 13,223,598 times
Reputation: 1734
Quote:
Originally Posted by studedude View Post
Sounds like it's idling slow enough that the alt doesn't know if it wants to put out or not. If you pick up engine speed about 100 RPM does the problem stop?
Yes if you pick up idle speed the flickering seems to go away...or possibly the frequency increases to the point that you don't notice it.
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Old 10-22-2009, 08:33 AM
 
Location: Kansas
3,855 posts, read 13,223,598 times
Reputation: 1734
Quote:
Originally Posted by sunsprit View Post
The flickering is a result of voltage surges.

This can be due to many possible factors, including a bad voltage regulator, an alternator that's not in good condition (possible bad diode, bad rotor/stator, poor internal connections), poor/high resistant charging system connections, poor/high resistant grounds, and also the idle surging is enough to cycle the alternator in/out of the charging system.

System voltage may not capture the fault. You need to check the wiring system wiring and connections for voltage drops (high resistant connections) with the voltmeter, or use a o'scope to capture the alternator voltage fluctuations that a voltmeter won't reveal.

If you aren't familiar with these types of tests, or don't have the equipment, then you'll need to take the car to an automotive electrical shop ... one that actually can test for the faults, as opposed to many shops that will simply start replacing parts.
Thanks! I'll start looking here.
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Old 10-23-2009, 12:38 AM
 
Location: Northeast Tennessee
7,305 posts, read 28,090,528 times
Reputation: 5523
I agree with Mitch... usually the voltage regulator causes this.
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