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flickering lights

PLATOKIDD

By PLATOKIDD
in Ask A GM Technician

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PLATOKIDD Enthusiast

PLATOKIDD

Posted
Posted

I have a 09 chevy 2500hd 6.0

The truck has a slight light flicker in most all of the lights(head lights , marker lights and interior lights.)
I checked the battery ground wire, cleaned all cables ends and mount surfaces, change the alternator and battery. Then a few days later the the lights are flickering again. 

Dealer tells me this is normal, power on demand or something like that. 

Any help here would be great, this is really starting to tic me off.

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Can you better describe what you mean by flickering?  To me I take it to mean the lights are never at the same brightness for longer than a second or two, regardless of engine speed or load.  The only time I have ever seen that was when the vehicle had a defective ground between the chasss and the body. 

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Yeah, I was just going to say pretty much the same thing. "Flicker" is very subjective, just like trying to describe sounds over the net.

 

That said, these trucks do have a sort of "on demand" charging system that's ECM controlled, which I also hate. I installed an Odyssey battery, since I have an air compressor system that will draw 60A at startup, and run at about 35A. I constantly have to maintain the battery with a 5-stage charger, since the ECM is looking for regular lead-acid battery voltage - it constantly thinks the system is charged, and lets it run down way too far for my liking.

 

Would LOVE to find a way to disable this stupid system!! A simple 1-wire alternator would work, but then the check engine light would be on - no go in communist Massachusetts. :mad:

 

 

Anyway, if you could post a video, that would be extremely helpful to you.

PLATOKIDD Enthusiast

PLATOKIDD

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7 hours ago, Doug_Scott said:

Can you better describe what you mean by flickering?  To me I take it to mean the lights are never at the same brightness for longer than a second or two, regardless of engine speed or load.  The only time I have ever seen that was when the vehicle had a defective ground between the chasss and the body. 

Yes and its more of a slight light flickering. Engine speed or load makes no dif.

Defective ground between the chasss and the body.?? Where would that be located?? 

 

 

PLATOKIDD Enthusiast

PLATOKIDD

Posted
  • Author
Posted
20 minutes ago, Jsdirt said:

Yeah, I was just going to say pretty much the same thing. "Flicker" is very subjective, just like trying to describe sounds over the net.

 

That said, these trucks do have a sort of "on demand" charging system that's ECM controlled, which I also hate. I installed an Odyssey battery, since I have an air compressor system that will draw 60A at startup, and run at about 35A. I constantly have to maintain the battery with a 5-stage charger, since the ECM is looking for regular lead-acid battery voltage - it constantly thinks the system is charged, and lets it run down way too far for my liking.

 

Would LOVE to find a way to disable this stupid system!! A simple 1-wire alternator would work, but then the check engine light would be on - no go in communist Massachusetts. :mad:

 

 

Anyway, if you could post a video, that would be extremely helpful to you.

Okay will try to get a video posted here later. 

 

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

I would also ask if there is any sort of pattern to the "flickering".  For example, does the flickering change in speed with changes in rpm, or load, or temperature etc.  Do you have any non OEM accessories like audio equipment, heated seats, exterior lighting(including running led type bulbs), trailer brake controller etc.  Finding a pattern to reproduce the condition every time will make diagnosis far easier. 

PLATOKIDD Enthusiast

PLATOKIDD

Posted
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Posted
3 minutes ago, Doug_Scott said:

I would also ask if there is any sort of pattern to the "flickering".  For example, does the flickering change in speed with changes in rpm, or load, or temperature etc.  Do you have any non OEM accessories like audio equipment, heated seats, exterior lighting(including running led type bulbs), trailer brake controller etc.  Finding a pattern to reproduce the condition every time will make diagnosis far easier. 

No pattern found, flickering don't change with speed or load and truck is all stock.

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted
7 minutes ago, PLATOKIDD said:

Yes and its more of a slight light flickering. Engine speed or load makes no dif.

Defective ground between the chasss and the body.?? Where would that be located?? 

 

 

Sometimes it as simple as the battery ground cable having a 10 or 12 gauge wire going to the body in addition to the heavy cable going to the engine.  It really does not matter where it is, as long as there is one. You could just add a 10 gauge or bigger wire from the engine to the chassis to the cab to ensure the grounds are good.  Take a good look at the crimped end of the battery ground cable for any white powdery stuff right at the crimp.  If the insulation at the crimp appears to be swollen, cut it open to see if it is corroded. 

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

One thing you can do to rule out the battery ground cable, is hook up a set of jumper cables to battery ground, and clamp them onto something clean and rust free (a tall order if you live in the salt belt), and see if the problem goes away. 

 

This will also work for any circuit. Doesn't have to be a wire as big as a jumper cable for the interior light circuit, but you get the idea. The interior light on a '09 is probably grounded by the BCM - would have to get a wiring diagram and see. 

 

EDIT: Just went through my notes: check the ground on the BACK of the passenger side cylinder head  - this is the main ground for the BCM. Also, there's another important ground on the driver's side body mount underneath, about where your left foot is when driving.

PLATOKIDD Enthusiast

PLATOKIDD

Posted
  • Author
Posted
55 minutes ago, Jsdirt said:

One thing you can do to rule out the battery ground cable, is hook up a set of jumper cables to battery ground, and clamp them onto something clean and rust free (a tall order if you live in the salt belt), and see if the problem goes away. 

 

This will also work for any circuit. Doesn't have to be a wire as big as a jumper cable for the interior light circuit, but you get the idea. The interior light on a '09 is probably grounded by the BCM - would have to get a wiring diagram and see. 

 

EDIT: Just went through my notes: check the ground on the BACK of the passenger side cylinder head  - this is the main ground for the BCM. Also, there's another important ground on the driver's side body mount underneath, about where your left foot is when driving.

Thanks, will give it a look when it warms up a bit. Too darn cold to leave the house.

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