Lights flickering/pulsating - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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  #1  
Old 11-06-2011, 11:41 PM
rdy2fly's Avatar
rdy2fly rdy2fly is offline
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2005 Isuzu Ascender
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Lights flickering/pulsating

Hey guys, new here and first post - I have a 2005 Isuzu Ascender (rebranded Envoy) that I've been fighting this light flickering/pulsing problem and am ready to pull my hair out. Headlights and interior dome lights will flicker (pulse) at a fairly steady rate, although it seems that the headlights do not do this at idle but the interior lights do. The intensity increases with rpms as far as I can tell. My alternator was recently replaced and still happens. I have a fairly new battery, and I've cleaned and tightened all connections and grounds that I can see. I don't have any aftermarket add-ons, and I know that it's not the 2nd air pump causing this as the fuses were pulled. I even took it to an automotive electrical shop and they're stumped as well. The flickering isn't dangerous, just annoying! I don't understand the HID enough to know if this would fix my headlamp pulsating problem, or make it worse. I can live with the interior dome lights doing this since they're rarely on, but driving down a dark highway and seeing this flickering is what is bothering me. I would appreciate any ideas, or if anyone else has experienced this. I absolutely love this vehicle - it's my 4WD Cadillac! But this light problem drives me crazy. Does anyone have any ideas? Thanks so much!
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  #2  
Old 11-07-2011, 10:47 AM
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the roadie the roadie is offline
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Do the high beams do this or just the lows? What's the frequency of the flicker? And do you mean by "intensity" that the depth of the flickering (from brightest to dimmest) gets larger with RPM, or the frequency (time between brightness changes) goes up with RPM? Do you or any engineering friends have an oscilloscope to look at the voltage and see its real behavior?
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  #3  
Old 11-07-2011, 11:09 AM
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rdy2fly rdy2fly is offline
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Thanks for the reply - The high beams do this as well, and it seems that all incandescent bulbs do it (interior as well) although I cannot tell whether or not the dash lights flicker like this. I'm assuming the tail lights do it as well. As far as the RPM's, it is the frequency that increases with the RPM's. Unfortunately I do not know anyone who has an oscilloscope. Now I will say this (if this makes any sense) - the exterior lights do not appear to be flickering at idle, although the interior dome lights do. When stepping on the gas, the exterior lights will start to flicker and the dome lights start flickering faster. It may be that it is harder to tell that the outside lights are flickering but it seems to be related. The flickering does not seem to increase as the RPM's go up, the flickering will "level off" if that makes any sense. I know this sounds really crazy
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Old 11-07-2011, 11:35 AM
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the roadie the roadie is offline
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Many auto electrical shops have scopes. How old is your battery? If your wires are good, a good battery will smooth out fluctuations and stop most flickering. If the battery is bad, AND there's a wiring issue, especially with grounds around the engine compartment, in my experience that's when flickering happens. But seriously, five minutes with an oscilloscope should be enough to figure it out without shotgunning.
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  #5  
Old 11-07-2011, 12:56 PM
SparkyJJO SparkyJJO is offline
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Another thing that came to mind is the rectifier in the alternator could be going out on you as well. Something else to test.
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  #6  
Old 11-12-2011, 08:26 AM
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tricguy007 tricguy007 is offline
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I also have this very annoying problem done everything that has been said above new battery,alt,cleaned everything possible, the only thing I've noticed is it gets worse the colder it gets , almost to the point at nite people are going to think I'm a cop, because coming to a stop my lights flash so much and my volt gauge floats at the same time
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Old 11-12-2011, 12:21 PM
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How fast does it move up and down, and what are the lowest and highest voltages seen? Use a voltmeter - don't trust the dash gauge.

Also check all grounds, not just the ones in the engine compartment.

http://forums.trailvoy.com/showthread.php?t=80661
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  #8  
Old 11-21-2011, 12:41 PM
sylvezter sylvezter is offline
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I have also had the same exact problem as the OP. The headlights, dash lights, and dome lights all flicker at idle and appear to increase with frequency at higher RPM. A volt meter shows voltage fluctuation from 12.8-14.2 volts. Usually the variation in voltage is less than 0.5 volts. The frequency of the cycling is roughly 5 times a second.

This problem was aggravated for me when my old battery was replaced. Before, I didn't notice the problem. The cycling flickering was almost entirely eliminated when I put the old battery back in, just barely noticeable in the interior dome lights. The voltage meter showed about 0.1 to 0.2 voltage fluctuations. Is this normal?

Why would a battery cause the electrical system to pulsate??? Could it be the old battery was just better filtering out the voltage fluctuations caused by a failing alternator? Or do I have a bad battery. The new battery passed the load test at Sears and shows to be good.
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  #9  
Old 11-22-2011, 09:15 PM
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tricguy007 tricguy007 is offline
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My voltage will go from 13.6 all the way down to 11.9 was the lowest I seen, it mostly happens when lifting off the gas and coming to a stop it drops, everything dims down and the as fast as it dims it comes back up to 13.5-13.7
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  #10  
Old 11-26-2011, 11:39 PM
dclamkin dclamkin is offline
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First post, and I'm really glad that somebody else has posted about this problem as it happens to me too. It doesn't happen as frequently as it sounds like it happens to others here, but it does happen. For some background I have a 05 TB LS that I purchased in December 2011. Although I have many plans for changes to the TB the only one I have completed was replacing the factory rearview with one that has the compass and temperature features. Is there anyway that the addition of the mirror is causing this? Maybe I didn't make a secure enough connection somewhere? Also me calling it flickering is sort of an understatement because when it happens in my TB it looks very much like I am flashing my highbeams at oncoming traffic. The flickering isn't a safety hazard at this time but it is problematic because it always seems to happen when I'm driving home from work around the same time as bar close and I am worried that the local authorities will pull me over one of these times thinking I am some drunk driver cruising down the road randomly flashing my lights at people. The officer will be rightfully doubtful when I tell him it is a malfunction in my TB and I will be wasting my time doing a field sobriety test.
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