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07 Tahoe with flickering headlights


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jlenkows's Avatar
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October 25th, 2010, 7:24 PM   #1  
07 Tahoe with flickering headlights

It's been a while since I've posted....

My 07 Tahoe (out of warranty) has come down with a case of flickering headlights and fog lights. The voltage gague is at 14 and the problem is happening mostly when coasting but sometimes when my foot is on the gas.

I have a feeling that the problem is the alternator, but I also saw some TSBs that resemble the issue, but didn't quite nail it on the head.

Anyone have this problem?? Anyone know what the cheap but proper fix is???

 
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October 25th, 2010, 9:21 PM   #2  
My best guess would be the alternator too. Or loose/dirty ground connection. Since when you coast, the engine settles in its no-load position. When you accelerate, the torque causes the engine to try to rotate and thereby moves slightly.

 
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October 25th, 2010, 9:52 PM   #3  
My 07 Tahoe headlights will just barely dim a bit and then brighten back up from time to time almost like an accessory(AC, or cooling fan) kicking on and then the alt kicks in and brings the voltage and current back inline...
It has done it even after I had the battery replaced, thou when I added my aux battery it seems to have gone away or become a lot less noticable.

It might be worth checking the grounds as shark suggested and maybe even checking / re-torquing the connection to the back of the alternator as well...

 
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October 25th, 2010, 11:54 PM   #4  
Have you had the 07 alternator software upgrade that was for battery rundown?

 
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October 26th, 2010, 10:40 AM   #5  
Im going to use the assume word and guess that when they replaced my battery they checked for the update...
I did ask about any updates for my vehicle a couple of oil changes back and the service advisor said I was good....
It would be nice to know what "rev" of software I have and to know what updates have been put in place...

I may give my service advisor a call this week and inquire a bit more....

 
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October 26th, 2010, 2:59 PM   #6  
I took a quick look at all of the connections and they all appear snug and clean. One thing I noticed is that the top of my battery is 'wet' and that one of the cell tops is a little up. Since it's a Sears battery less than a year old, I'll be heading there for them to tell me that there's nothing wrong with it.

As for the software update -- I'm pretty certain it was done already, but I'll give the dealership a call to make sure.

Thanks for all of the ideas!!

 
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October 26th, 2010, 8:35 PM   #7  
Posted By: in2pro Im going to use the assume word and guess that when they replaced my battery they checked for the update...
I did ask about any updates for my vehicle a couple of oil changes back and the service advisor said I was good....
It would be nice to know what "rev" of software I have and to know what updates have been put in place...

I may give my service advisor a call this week and inquire a bit more....
The update was primarily to "fix" the quick rundown of the battery when listening to the radio. Before the update, my '07 would require a jump start after three 10 min retained electrical power cycles. Never checked after the update but it was more than five.

There might be some info on this forum in some old threads. Just checked my '07's service records and all it said was "07033 battery rundown, expires w/ base warranty, reprogram the BCM"

 
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November 15th, 2010, 8:08 AM   #8  
Sears, as expected, said the battery was fine... They tested the alternator and it too came back OK....

The problem appears to be getting worse -- all of the lighting is noticably flickering now.

I spent some time under the hood checking coil packs and wires -- all looked OK.

Popped open the power center and found the relay for the LOW FAN was up a bit -- re-seated it and testing the lights. no flicker. Could I have possibly fixed the problem???

After 20 minutes of testing, the flickering was gone.

I covered the power center up and did a final test.

It's flickering again.

My next step is to disconnect the battery and pop the power center open to check the grounds in there.

I also put a call into my dealership's service manager to see if he has any thoughts, TSBs, or known fixes.

It figures that the month after I pay the truck off, problems start happening.

 
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November 15th, 2010, 10:40 AM   #9  
Post some pictures of the fuse box removal if possible....

 
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November 15th, 2010, 7:00 PM   #10  
My 07 was doing this same thing but not as severe as you discribe. I ended up replacing the battery as well as all of the battery cables. I also cleaned all of the terminal connections before torqing everything down.

Also, I would not put too much faith in Sears being able to correctly asses the status of your alt? I've been told it takes a certain type of alt tester to get an accurate read on it? In a nutshell the alt is controlled by the BCM which senses when a load is applied to the battery. Once this happens the BCM tells the alt to charge the battery. This is how it was explained to me since my tester kept showing the alt as failing four out of five times.

One other thing, any battery that has a bulge in the casing has overheated which is usually caused by a runaway alt or battery charger. I replace any battery on my generators that show this type of damage.

Right now my 07 is no longer doing the flickering however I am interested in the battery run-down software upgrade.

Good luck.

 
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