Flickering lights

[solli5pack]

Hey everyone. So I've been dealing with flickering lights for the past few months on my 08 Yukon and so far haven't been able to figure them out. All the exterior and interior lights flicker and I believe the dash lights flicker also so pretty much the entire truck. I replaced all the battery cables with GM parts, replaced the alternator twice with the one of Amazon that @Geotrash recommends often and tested all the grounds in the engine bay for voltage drop and all tested good. I even pulled the front bumper to inspect and clean the ground locations on the support. So far nothing has worked and I'm stumped. The battery came with the truck when I bought it a year and a half ago so unsure of the age but the battery only starts the truck right? So how could it cause flickering? I have the Suburban so I guess I could start swapping some stuff like headligh switch or relays to see if it helps but I'd rather not. No voltage drops at all when the trucks running. Also the flickering seems to be directly related to when the engine RPM's increase wether driving or parked. I did find corrosion in almost everything I replaced. I think this truck spent a lot of time at the Jersey shore with its previous owners.See below. So many times I thought I solved it. Any ideas?

 

[Doubeleive]

all that corrosion is 100% percent a problem
I would replace the battery and add a few Fresh grounds that should eliminate any flickering.
and yes a weak battery can most definitely cause flickering so can poor grounds AND poor voltage
you might be showing 12volts, but there may be low amps (poor electrical connection)
these trucks do not like low voltage

 

[solli5pack]

all that corrosion is 100% percent a problem
I would replace the battery and add a few Fresh grounds that should eliminate any flickering.
and yes a weak battery can most definitely cause flickering so can poor grounds AND poor voltage
you might be showing 12volts, but there may be low amps (poor electrical connection)
these trucks do not like low voltage

Ok thanks. Quick look on Autozone and a battery is like $200 now so I'm gonna swap in the one from my Burb to see if anything changes. I'm gonna replace the ground to the under hood fuse box even thought it tested good and see what happens. I feel like it's something with the fuse box since everything seems to be affected. Under hood fuse box looks good BTW, no corrosion at all except for the cable from the **** fuse which I replaced. Is there any actual troubleshooting process to something like this? Like I said all voltages check fine with a meter and no stray voltage on any of the grounds.

 

[Doubeleive]

Ok thanks. Quick look on Autozone and a battery is like $200 now so I'm gonna swap in the one from my Burb to see if anything changes. I'm gonna replace the ground to the under hood fuse box even thought it tested good and see what happens. I feel like it's something with the fuse box since everything seems to be affected. Under hood fuse box looks good BTW, no corrosion at all except for the cable from the **** fuse which I replaced. Is there any actual troubleshooting process to something like this? Like I said all voltages check fine with a meter and no stray voltage on any of the grounds.

the best way to troubleshoot it yourself is to get a meter out and start OHM testing everything you can access, all grounds should be 0 ohm's (I would say anything over .02 ohm is questionable) to the battery post's. especially in and around the engine bay. when you hit a poor connection you will know. if you get high ohm's, clean it :wire brush/sandpaper/whatever. then re-check
your picture of that corrosion would make me really look at the associated cables they can corrode like that on the inside and look fine on the outside. that is a known problem even on the newer trucks
look around your starter cables also make sure nothing is grounding out there have been reports and I have experienced it myself where the power cable to the starter is burnt and shorting out on the heat shroud or anything around it. I was just under my 2012 a couple weeks ago and the starter solenoid heat shroud had slide down and was wearing a spot on the starter power cable. if that happens it can cause flickering like you are having or much worse.

 

[Doubeleive]

you can also use your meter and check stuff for 12v while it is running and under a load, so like start it up and turn a bunch of stuff on, headlights, heater/ac, seat heater, radio, defroster, etc and see if the voltage drops, turning those things on should make the alternator kick up and you should have mostly 13.4v (or more) at the battery post's

 

[mikez71]

flickering with engine off?

flickering with old alternator as well?

 

[Fless]

I hope that the pics of the Mega Fuse connections are the "before" pics.

 

[solli5pack]

I hope that the pics of the Mega Fuse connections are the "before" pics.

Yes. I tried cleaning them but still flickering so replaced everything. That terminal comes with the GM replacement cable that runs to the fuse box. The new fuse looks rusted but it's not..the brass came that color from the factory.

 

[solli5pack]

flickering with engine off?

flickering with old alternator as well?

I never checked with the engine off...I will tonight but since the flickering seems to be cause by increased RPM'S of the engine I doubt it. I'm gonna have a few cold ones after dinner and do some resistance checks on my engine grounds.

 

[B-train]

It's probably the alternator. The original on my 2008 Denali started doing that on a trip from CA to WI in 2021......kind of unnerving at 1:00 a.m. But, it didn't stop working. I put a new lifetime alternator from Carquest and the flickering stopped. Been 50k miles and no issues.

But, as others have suggested, cleaning the connections is a good practice and, based on your pictures, was worthwhile.