Need some help solving electrical flickering

#83
Near/behind the battery is what I've seen reported. I don't know for sure.
 

MRRSM

Gold Supporter
#85
I was wondering if there might also be a Mechanical Cause that is directly involved with the Charging System, This video gives a very interesting look at and explanation of two other possible causes towards the very end of the film that are worth seeing:

 
#86
So the SARVC is the EPM I was talking about. EPM = Electrical Power Managnent. The sensor is on the negative battery side. I went over that post, not sure what I’m suppose to do from it?

I did unplug the EPM once and the flickering continued. A replacement EPM which is the whole negative battery cable is $90+. Nothing points to it specifically though to replace it.
 
#87
I was wondering if there might also be a Mechanical Cause that is directly involved with the Charging System, This video gives a very interesting look at and explanation of two other possible causes towards the very end of the film that are worth seeing:

Good video, i do have a new belt. Even tried different sizes I had on hand, no change.
 

MRRSM

Gold Supporter
#88
NP... But I'd Bet Coin that your OEM Serpentine Belt Tensioner has seen better days... That Power Plant you have looks Pretty Mean and Punchy in your Profile... and I'd also bet that when you press down on the "Green Means Go... Pad" ... the wound coiled steel spring inside that thing down there sheds blood. FWIW... This ACDelco Pro Version is on Sale right now via this Link... Just something simple to R&R and to check off a box on your WTFIW? list... ;>)

https://www.amazon.com/ACDelco-38158-Professional-Automatic-Tensioner/dp/B000C9PFJK/ref=au_as_r?_encoding=UTF8&Make=Chevrolet|47&Model=Trailblazer|489&Year=2007|2007&ie=UTF8&n=15684181&newVehicle=1&s=automotive&vehicleId=1&vehicleType=automotive

Here is another link on the controversial topic about the effects of using Different Length Serpentine Belts and the effects of Transitional and Angular Velocities related to the way these impact upon accessory components via stress and strain... wear and tear:

https://gmtnation.com/forums/threads/can-a-5-mm-shorter-serpentine-belt-cause-problems.14227/
 
Last edited:
#89
NP... But I'd Bet Coin that your OEM Serpentine Belt Tensioner has seen better days... That Power Plant you have looks Pretty Mean and Punchy in your Profile... and I'd also bet that when you press down on the "Green Means Go... Pad" ... the wound coiled steel spring inside that thing down there sheds blood. FWIW... This ACDelco Pro Version is on Sale right now via this Link... Just something simple to R&R and to check off a box on your WTFIW? list... ;>)

https://www.amazon.com/ACDelco-38158-Professional-Automatic-Tensioner/dp/B000C9PFJK/ref=au_as_r?_encoding=UTF8&Make=Chevrolet|47&Model=Trailblazer|489&Year=2007|2007&ie=UTF8&n=15684181&newVehicle=1&s=automotive&vehicleId=1&vehicleType=automotive
I just upgraded to a brand new HD tensioner from Magnuson recently so I know I’m good there. My original tensioner is in good shape, it only has 46,000 miles on it. There was no change with the flickering between the original and HD.

I really didn’t think the flickering was tensioner related anyway when I did the swap. I did it for more tension on the S/C pulley if anything. Even though I’m not experiencing any slip with my 2.9”. Figured I would in time.
 
Last edited:
#90
I know you replaced the alternator but maybe take it in for testing. Maybe it`s a dud. it happens.
 

MRRSM

Gold Supporter
#91
Take a look at THIS:

http://www.tbssowners.com/forums/tsb-recall-sections/224434-headlight-relay-2008-tbss-print.html

https://www.amazon.com/dp/B0065S6S8Y/ref=cm_sw_r_cp_api_v-2pzbVV63X85#customerReviews

Here are (2) of (189) Customer Reviews from Amazon:

5.0 out of 5 stars Replacement for 2008 Envoy Denali -- headlight relay module
ByEngrKaton January 20, 2015
Verified Purchase
Purchased for an 2008 Envoy Denali which had intermittent low beam issues. Was an easy drop in replacement. Been installed for a couple of months now and the issue has not resurfaced.

4.0 out of 5 stars ACDelco 15016745 OE Service Headlamp Relay
ByRRon January 20, 2014
Verified Purchase
One time on the freeway at night ...both my low beams flickered. About a week later, both my low beams died while pulling into my neighborhood. I was aware this relay is known to fail so I replaced it. Have not had any problems since.


TBSSRELAY.jpeg
 
Last edited:
#92
He did say that ALL his lights flicker, not just the headlights, pulled the relay, same. But when he disconnects the alternator, it stops so it's not a draw or relay issue but something with the alternator or charging system.

My last suggestion still stands.
 
#93
I know you replaced the alternator but maybe take it in for testing. Maybe it`s a dud. it happens.
I’ve tried two and had them both bench tested. Odds of it being an alternator is very slim. The original poster of this did the same as me and even got lucky enough to borrow a brand new OEM GM alternator, same issue. I’d bet the price of the OEM GM alternator I would get the same issue still even though it make absolutely no sense to me.
 
Last edited:
#94
Take a look at THIS:

http://www.tbssowners.com/forums/tsb-recall-sections/224434-headlight-relay-2008-tbss-print.html

https://www.amazon.com/dp/B0065S6S8Y/ref=cm_sw_r_cp_api_v-2pzbVV63X85#customerReviews

Here are (2) of (189) Customer Reviews from Amazon:

5.0 out of 5 stars Replacement for 2008 Envoy Denali -- headlight relay module
ByEngrKaton January 20, 2015
Verified Purchase
Purchased for an 2008 Envoy Denali which had intermittent low beam issues. Was an easy drop in replacement. Been installed for a couple of months now and the issue has not resurfaced.

4.0 out of 5 stars ACDelco 15016745 OE Service Headlamp Relay
ByRRon January 20, 2014
Verified Purchase
One time on the freeway at night ...both my low beams flickered. About a week later, both my low beams died while pulling into my neighborhood. I was aware this relay is known to fail so I replaced it. Have not had any problems since.


View attachment 83226
I swapped around relays and even tried a new relay, no luck. My problem isn’t isolated to the headlights... it’s taillights, interior lights, lisence plate lights, all lights.
 
#96

That brings up a good point and I just about upgraded my alternator to a much bigger unit since mine is a 145amp. From What I’ve researched, since my 2007 has that EPM or SARVC, whatever you want to call it. Since the alternator output is completely controlled by the BCM (or whatever) it doesn’t matter if you have stock or a 300 amp alternator, the BCM will only allow a certain amount to be used. So in my case it would be completely worthless. I talked to 3 completely different sources about this and got this same answer. Unless a 2007-2009 TB guy can respond and disprove this I’m at another dead end.

What bothers me the most is the OP had this same issue. And tried Reman and new alternators and had this same issue and never solved it.

I’m beginning to think this will remain unsolved.
 
Last edited:
#97
I was also told the ignition switch could cause the flickering lights I’m experiancing. I have yet to find anyone who had the flickering light issue and the ignition switch fixed it though. Thoughts?

I’m sure it will be another dead end just like all the dead end threads out there in google land.
 

MRRSM

Gold Supporter
#98
Here are a Few More Ideas for you to Beat Hell out of…

In the later model Trailblazers and Envoys… When running in Daylight Driving Mode… The Headlights use PWM (Pulse Width Modulation) at around a 70% Duty Cycle ...and that can make them appear to ‘flicker’. Investigating “What’s Up?” with that circuit might lead to other discoveries of sub-electrical system components that are doing likewise… but at night time.... when the problem would be most apparent.

Next… On the subject of Parasitic Draw/Drain as being a possible contender involved by way of weakening your over night battery storage:

http://flashoffroad.com/electrical/CurrentDrain/currentdrain.pdf

Parasitic Drain Tester:

https://www.amazon.com/s/?ie=UTF8&k...qmt=p&hvbmt=bp&hvdev=c&ref=pd_sl_4ch3xyje3h_p

And on the Subject of “What is ‘Normal Parasitic Drain’..?”:

If you have a decent Wiring Diagram... try to locate the positions of Ground #102 and #201 and after removing them and cleaning them right down to bare metal and re-attaching them with a drop of Dielectric Grease... perhaps approaching this problem "From the Grounds Up" ...might cast a brighter light on the solution:

GROUND102.jpeg
 
Last edited:
#99
Here are a Few More Ideas for you to Beat Hell out of…

In the later model Trailblazers and Envoys… When running in Daylight Driving Mode… The Headlights use PWM (Pulse Width Modulation) at around a 70% Duty Cycle ...and that can make them appear to ‘flicker’. Investigating “What’s Up?” with that circuit might lead to other discoveries of sub-electrical system components that are doing likewise… but at night time.... when the problem would be most apparent.

Next… On the subject of Parasitic Draw/Drain as being a possible contender involved by way of weakening your over night battery storage:

http://flashoffroad.com/electrical/CurrentDrain/currentdrain.pdf

Parasitic Drain Tester:

https://www.amazon.com/s/?ie=UTF8&k...qmt=p&hvbmt=bp&hvdev=c&ref=pd_sl_4ch3xyje3h_p

And on the Subject of “What is ‘Normal Parasitic Drain’..?”:

If you have a decent Wiring Diagram... try to locate the positions of Ground #102 and #201 and after removing them and cleaning them right down to bare metal and re-attaching them with a drop of Dielectric Grease... perhaps approaching this problem "From the Grounds Up" ...might cast a brighter light on the solution:

View attachment 83245

I’ve already cleaned off and barely metaled #201, #102, and the main interior grounding point.
 
Well tonight I decided to try a brand new ignition switch since it’s been linked many odd issues on this platform. And of course is did NOT fix my flickering issue.
 

MRRSM

Gold Supporter
There might be two other places that you should contact to sort this issue out. Up until the last few minutes... after having just read your entire Profile... we have been laboring and basing our reactions and responses to your questions as though your engine and hardware were "Stock as A Clock"... But since you are running a Supercharger set up...with alterations in your Pulley System and additional frictional and power draw downs happening... as well as using PCMofNC after-market harnessing... You would be better off consulting Lingenfelter-Magnusson and PCMofNC or even some other forums that strictly deal with your present high performance engine layout and seek your answers from people with highly modified engines... people with experience with all of the problems that come right along with building them. And so this means that with your Non-Stock Set-Up... This is NOT "Just like every TB flickering light thread, unsolved."
 
Last edited:
I had the flickering issue for quite sometime before I did any mods to it. The mods I did are not the cause of this at all, Wish it was that simple. The truck was bone stock until the winter of 2015.

Furthermore I disabled all the electrical add ons recently to eliminate those (even though it was a waste of time honestly) and there was no change as expected. Only thing the supercharger setup did was add 150 more HP and knocked off 2 secs off the quarter mile time. (Yes I have slips to prove this, this ain’t my first build by far) Nothing I added on caused this or made it worse period. My symptoms mirror what the original poster of this thread had years ago. Curious what happened there or if he traded it off.

The reason I have not tried to fix it all is because I hardly drive it and not much at night. It’s been a fair weather truck all it’s life. It has seen rain 5 times in its life and never snow. It’s arguably the cleanest TBSS in this part of the country. It only has 46k on it as it sits today.

Anyway the problem has been there and I’m sick of the issue I want to fix it. I’ve found several threads on google with the same issue, no one on the internet has yet to solve it or if they did it’s a big secret no one will let go. You’d think since 2002 the cat would be out of the bag.

My truck is nearly flawless except for this one flaw. Frustrating having such a nearly perfect vehicle with one flaw that cannot be solved by no one.

BTW, I’m not some 16 yr old that’s never worked on a car before. I consider myself a fairly mechanically inclined middle aged car guy. I have several car builds out there running around from supercharged to Nitrous builds (there’s a 10sec Nitrous GTO parked with my TBSS right now which is my other toy) Not going to say I’m an electrical genius by far but I’ve done my fair share.

I figured people would blame the mods for the issue but it’s simply not the case. This is a different issue.
 
Last edited:
Well I tried something else today since I’m a pioneer on this adventure. I took the alternator off my 2013 Silverado 6.2 L9H which comes from the factory with a 145 amp alternator. It’s OEM and only had 39k on it. The only main difference is this alternator is NOT a clutch drive like what comes in the TBSS.

Anyways I really didn’t want to tear apart my truck but I bit the bullet. As for the results.... it still flickers however I don’t think it’s as bad though. But I still see it in the interior lights, headlights, tail lights, license plate lights, etc. Now I kinda wish I could borrow a high amp alternator without spending $500 on a guess.

What doesn’t make sense, other TBSS run around with the same aftermarket stuff that I do. Stock TBSS run around with no issues either. Why would Myself and the original poster need a bigger alternator while others do not? Stock or not? There’s your $500 question right there. Who wants to take a stab at this one?
 
What do you mean a "clutch drive"? Never heard of that on an alternator.

So just taking a wild stab. Could it be the voltage sensing wire that's wonky? Bad contact or wire? Obviously the alternator is doing this for some reason.
 

MRRSM

Gold Supporter
IIANM one of our better known Members… @MAY03LT had made some major changes to his power set up with the advent of some bigger sound amplification… you can actually see some of what his under-hood wiring looks like in how robust his changes were… perhaps he has some of his videos over on his Youtube Channel that will address this as well.

You’ll recognize this as your own quote posted on another forum on 02/12/2018 in your quest to solve this annoyance… and it actually gives some important clues that bear out @Mooseman ‘s suspicion of a sketchy Alternator Signal Wire. It also might return the attention to the need for a different kind of battery if the one in-dwelling has hidden dead cell or over-charging damage issues.

Well, I just tried throughly cleaning grounds 102 and 201 and the grounding block under the console on the inside, no change. Even disconnected all the extras I added such as the efans, alky injection, IC pump, etc, no change.

Also decided to try for shits and giggles... removing the belt there is no flicker. Removing the battery power wire on the alternator no flicker. Yet if I swap alternators again it will still flicker. Makes absolutely no sense at all. Only thing I wonder, with the minor electrical additions I have do I need a bigger HO alternator? Other than that I have nothing.”

http://www.tbssowners.com/forums/el...-flickering-light-issues-need-help-print.html
 
What do you mean a "clutch drive"? Never heard of that on an alternator.

So just taking a wild stab. Could it be the voltage sensing wire that's wonky? Bad contact or wire? Obviously the alternator is doing this for some reason.
For some reason the 2007-2009 TBSS has the clutch style alternator. I believe the Vettes had it too. I think my GTO has it as well but I’ve honestly never messed with it. Either way I think it’s more shit to go wrong and it’s not on anything newer that I know of.

If your talking about the EPM, I’ve tried disconnecting that with no luck. It’s still odd that disconnecting the alternator power wire there’s no flicker and my OEM alternator from my Silverado makes it not as bad. Two remans and it flickers like crazy. Makes no sense.
 
IIANM one of our better known Members… @MAY03LT had made some major changes to his power set up with the advent of some bigger sound amplification… you can actually see some of what his under-hood wiring looks like in how robust his changes were… perhaps he has some of his videos over on his Youtube Channel that will address this as well.

You’ll recognize this as your own quote posted on another forum on 02/12/2018 in your quest to solve this annoyance… and it actually gives some important clues that bear out @Mooseman ‘s suspicion of a sketchy Alternator Signal Wire. It also might return the attention to the need for a different kind of battery if the one in-dwelling has hidden dead cell or over-charging damage issues.

Well, I just tried throughly cleaning grounds 102 and 201 and the grounding block under the console on the inside, no change. Even disconnected all the extras I added such as the efans, alky injection, IC pump, etc, no change.

Also decided to try for shits and giggles... removing the belt there is no flicker. Removing the battery power wire on the alternator no flicker. Yet if I swap alternators again it will still flicker. Makes absolutely no sense at all. Only thing I wonder, with the minor electrical additions I have do I need a bigger HO alternator? Other than that I have nothing.”

http://www.tbssowners.com/forums/el...-flickering-light-issues-need-help-print.html

I’ve seen some of MAY04LT videos. Pretty good stuff. I like his no BS approach, I think it’s gonna take more than LEDs to fix my problem however. I’m curious what size alternator he ended up with.

As far as the other quote from TBSSOWNERS I mentioned earlier in this thread I installed a brand new battery a week or two ago. I went with a good AGM battery this time around.

I didn’t get much of any input from TBSSOWNERS. I also posted on TrailVoy with nothing at all. This is the only place I’m actually getting a response therefore this is the only place I’ve beeb updating.

As far as the alternator wire being bad.... Good point, however I have the big 3 done so it wouldn’t matter. Not only do I have the OEM alternator wire but I have a wire that goes directly from the alternator to the battery. I’ve also tried disconnecting either one and the problem is still the same. That should conclude my alternator wire is good.

On some other platforms people cut off the end of the OEM alternator wire and tape it off to not use it and only relay on the power wire between the alternator and the battery of there big 3. Not wise in my opinion and it doesn’t honestly hurt a thing running both (though some will argue that), I’ve had no issue in all the other cars I’ve done over the years. And yes I’ve removed the big 3 for testing purposes to conclude that this is not my issue on my TBSS. Obviously no change either way.
 

MRRSM

Gold Supporter
This is yet another Long Shot Suggestion.... But what about replacing your Fuse Box Junction... Lock, Stock and Barrel... and Start Fresh where all of these competing electrical connections 'Hover Under Cover' and see if that makes any difference. Perhaps you can pick one up that is newer with a full set of Relays and Fuses...and not transfer anything from the Old Unit during this Heart Transplant?
 
Mini hijack. I just learned today about Alternator Decoupler Pulleys or clutches. Sounds like a good idea but just another thing to break or replace with the belt and tensioner.


This is yet another Long Shot Suggestion.... But what about replacing your Fuse Box Junction... Lock, Stock and Barrel... and Start Fresh where all of these competing electrical connections 'Hover Under Cover' and see if that makes any difference. Perhaps you can pick one up that is newer with a full set of Relays and Fuses...and not transfer anything from the Old Unit during this Heart Transplant?
Probably a pricey shot in the dark. First, TBSS's are difficult to find in yards and second, a new one is probably a few bills. Kind of a drastic measure for a problem it might not even solve. Possible that a 5.3L box and harness is the same.
 

xavierny25

Well-Known Member
Even smaller hijack. My brother-in-law has an 08 tbss that i drive and work on all the time it's pretty bone stock with the addition of an after market amp,sub and speakers all the way around and we have never experienced this at all. The only time is we do get the lights to go dim on the dash is when we hit the window button and the window is maxed out to the top. Then again my 08 Envoy does the same.

On both the Voy and tb when we got our music thumping at high volume because of the bass is when we could get the headlights to dim down a bit. We aren't running high output alternators or batteries just 5fared caps. He's got just over 75000 miles on his and I've got just shy of 165000 on mine.
 
This is yet another Long Shot Suggestion.... But what about replacing your Fuse Box Junction... Lock, Stock and Barrel... and Start Fresh where all of these competing electrical connections 'Hover Under Cover' and see if that makes any difference. Perhaps you can pick one up that is newer with a full set of Relays and Fuses...and not transfer anything from the Old Unit during this Heart Transplant?

I’ve actually thought about this as a next move. It’s about a $500 gamble though and it’s a shot in the dark. Beside the fuse box, ECM, or TCM I have no idea what else it could be.
 
Mini hijack. I just learned today about Alternator Decoupler Pulleys or clutches. Sounds like a good idea but just another thing to break or replace with the belt and tensioner.




Probably a pricey shot in the dark. First, TBSS's are difficult to find in yards and second, a new one is probably a few bills. Kind of a drastic measure for a problem it might not even solve. Possible that a 5.3L box and harness is the same.

Exactly, more shit to go wrong. I’d rather have a regular alternator myself.

Not sure what the fuse box all interchanges with, pricey either way.
 
Even smaller hijack. My brother-in-law has an 08 tbss that i drive and work on all the time it's pretty bone stock with the addition of an after market amp,sub and speakers all the way around and we have never experienced this at all. The only time is we do get the lights to go dim on the dash is when we hit the window button and the window is maxed out to the top. Then again my 08 Envoy does the same.

On both the Voy and tb when we got our music thumping at high volume because of the bass is when we could get the headlights to dim down a bit. We aren't running high output alternators or batteries just 5fared caps. He's got just over 75000 miles on his and I've got just shy of 165000 on mine.

Yep. There are many other TBSS out there in the world running the same shit I’m running it no issues. Makes no sense to me at all. Like i said, another alternator would likely not solve anything for me.
 
No new updates otherwise. Unless I can find someone nice enough to loan me a 2007 TBSS fuse box (yeah right!) or I spend $500 for one I’m shit out of luck.

On a brighter note, I was at the track with my other car and made a few passes on the TBSS and got a PB of 12.10 @ 114 mph. She runs her ass off, she just wants to flicker at night. Can’t win then all I guess.
 
If it comes down to cases... you can always unbolt "The Big Box" and after pulling the sub-assembly connectors out... Shine a bright flashlight down the matrices of all of them and look fro any signs of burning or melting. CRC has a powerful Electric Circuit and Component Spray Solvent that would not hurt a thing by going everything and cleaning both side of the Fuse Block Mate Ups. The other thing to keep at your elbow is a complete list of Fuses and Relays to compare with the ones that you have with whatever is on this Long List from RockAuto.... and replace whatever does not meet with your approval... or that of your DMM:

https://www.rockauto.com/en/catalog/chevrolet,2007,trailblazer,6.0l+v8,1434296,electrical,fuse,2676