SOLVED - 2014 Suburban Electrical gremlins

[bacon612]

Hello everyone. Just realized that this sub exists. I've been troubleshooting an electrical issue on my suburban where my radio cuts out, I have headlight and interior lights flickering as well as some unstable and high voltage.

Truck has 125k miles. Things I have done so far...
New battery
New OEM Delco alternator
New OEM negative battery wire (runs to cylinder head and lower rad support)
Cleaned grounds on lower rad support (right and left side)
Cleaned ground under drivers seat on frame
Replaced ground strap on left side of firewall to rear of engine block.
Added another ground from the same stud mentioned above (left side of firewall) to a bolt under the alternator mount.

I know that the voltage regulator on these trucks is computer controlled and varies based on a bunch of things but I am seeing voltage bounce from 14.4 to high 15s and as mentioned above, I have some flicker and my radio cuts occasionally. This to me indicates that I've got something going on.

Anyone have anything similar happening?

 

[Joseph Garcia]

There is a ground on the driver's side frame under the truck around the driver's seat location that many electrical items are tied into.

 

[bacon612]

So I undid that ground cleaned it up and reattached. No difference. I read that there's another ground on the frame rail under front passenger seat but don't see it.

 

[bacon612]

Adding some info here. Still no solution and have some questions for testing methodology.

I have spent some time with South Main Auto and ScannerDanner youtube regarding voltage drop testing and its importance vs using the ohm meter function of my multimeter to test circuits.

I now know why voltage in these trucks when 'awake' (opening a door and dome lights lit) affects resistance testing with the ohm meter.
I also now know that these tests aren't helping me any because there isnt enough current in the wires during these tests to effectively show me any potential issues in these circuits.

So... now I am conducting voltage drop tests.

Because my issue is affecting headlights, the radio, interior lights, I am led to believe that my issue is caused by a main cable. Battery ground to engine block or positive battery terminal to fuse block. Is this true? Is it still possible that a connection on a minor circuit could be causing my issue?

What is considered to be enough load to effectively test voltage drop on these major cables?

I just turned headlights on and with a probe on the negative terminal of my battery, tested the positive terminal on the fuse block for voltage drop and didnt find any. I also ran a test with the headlights on and one probe at the positive battery terminal and tested a few different ground points. Also no voltage drop.

I am looking for some direction on how to continue my tests in hopes of finding my issue. Does anyone have any insight?

 

[Doubeleive]

Adding some info here. Still no solution and have some questions for testing methodology.

I have spent some time with South Main Auto and ScannerDanner youtube regarding voltage drop testing and its importance vs using the ohm meter function of my multimeter to test circuits.

I now know why voltage in these trucks when 'awake' (opening a door and dome lights lit) affects resistance testing with the ohm meter.
I also now know that these tests aren't helping me any because there isnt enough current in the wires during these tests to effectively show me any potential issues in these circuits.

So... now I am conducting voltage drop tests.

Because my issue is affecting headlights, the radio, interior lights, I am led to believe that my issue is caused by a main cable. Battery ground to engine block or positive battery terminal to fuse block. Is this true? Is it still possible that a connection on a minor circuit could be causing my issue?

What is considered to be enough load to effectively test voltage drop on these major cables?

I just turned headlights on and with a probe on the negative terminal of my battery, tested the positive terminal on the fuse block for voltage drop and didnt find any. I also ran a test with the headlights on and one probe at the positive battery terminal and tested a few different ground points. Also no voltage drop.

I am looking for some direction on how to continue my tests in hopes of finding my issue. Does anyone have any insight?

have you pulled the fuse box and inspected it on the bottom?
and one member found a corroded wire in the passenger side dash, behind the passenger side end cap that you can access with the passenger door open, just like the driver side one. one of the connectors was corroded and the flickering stopped once it was cleaned up. might be worth a check but unlikely to be the same scenario.....

 

[bacon612]

have you pulled the fuse box and inspected it on the bottom?
and one member found a corroded wire in the passenger side dash, behind the passenger side end cap that you can access with the passenger door open, just like the driver side one. one of the connectors was corroded and the flickering stopped once it was cleaned up. might be worth a check but unlikely to be the same scenario.....

I have pulled the fuse box. Looks pretty clean. Fought both coming out and back in again and broke one side of one of the grey retention clips. It seats in fine but i will need to look for a spare one now.

I was posting in the other thread where @solli5pack found that corrosion and came back here as not to hijack it. I did check the same connections next to the glove box and they were all clean. I guess the corrosion on one of those connections was important enough to cause an issue similar to mine. I wonder where my issue is

 

[Doubeleive]

I have pulled the fuse box. Looks pretty clean. Fought both coming out and back in again and broke one side of one of the grey retention clips. It seats in fine but i will need to look for a spare one now.

I was posting in the other thread where @solli5pack found that corrosion and came back here as not to hijack it. I did check the same connections next to the glove box and they were all clean. I guess the corrosion on one of those connections was important enough to cause an issue similar to mine. I wonder where my issue is

Check the dome lights that has came up before, grounding out on the body. kind of picking at straws here.
also you might get under it and take a good luck at the starter cable and solenoid, that can burn up and the heat shroud on mine was tilted down and started to bite into the starter cable but hadn't got past the insulation yet.
headlight grounds are on the frame/bumper under the radiator I believe you have to pull the front bumper cover to access them.

 

[bacon612]

Check the dome lights that has came up before, grounding out on the body. kind of picking at straws here.
also you might get under it and take a good luck at the starter cable and solenoid, that can burn up and the heat shroud on mine was tilted down and started to bite into the starter cable but hadn't got past the insulation yet.
headlight grounds are on the frame/bumper under the radiator I believe you have to pull the front bumper cover to access them.

So i did actually take the bumper off when i replaced the main negative cable from the battery. It has one main lead to the cylinder head and a small one that attaches to the front right side of the bumper. Everything under there including the left side looked really clean.

I did get under the truck and check the positive wire down to the starter. Though not the best picture, here it is. I wiggled it and it seems solid. Its the original starter and I have no issues cranking. Truck starts with ease. Is the fact that there is some bare copper between the insulation and the crimp an issue?

 

[Doubeleive]

So i did actually take the bumper off when i replaced the main negative cable from the battery. It has one main lead to the cylinder head and a small one that attaches to the front right side of the bumper. Everything under there including the left side looked really clean.

I did get under the truck and check the positive wire down to the starter. Though not the best picture, here it is. I wiggled it and it seems solid. Its the original starter and I have no issues cranking. Truck starts with ease. Is the fact that there is some bare copper between the insulation and the crimp an issue?

View attachment 440512

it's fine as long as nothing is touching it
have you checked the tail lights & harness?
and harness up in the top of the rear hatch that passes thru from the body to the hatch? it can wear thru and rub on the body
also check in your engine compartment all wiring especially anything that sits on, touches or lays on anything, feel the wires with your hand on the bottom to check for any worn spots

 

[bacon612]

That was kind of my thought. I found the oem replacement cable for $64 on amazon but dont want to continue guessing.

I just did 2 voltage drop tests starting the truck.
1) from the positive battery terminal to the engine block ground at the cylinder head. Result was Max 14.9 volts and min 10.68.
2) from the negative battery terminal to the ring terminal at the end of the starter positive cable at the starter. Max was also 14.84 and min was 10.4.

This doesn't seem like a meaningful difference does it?

My next step is to drop the dome light housing and look around in there. Fingers crossed I dont break the plastic