2007 Silverado 6.0 2WD. For the past couple of months, I have noticed the all the lights, headlights and interior, flicker when idling. After searching, the most common cause found was a bad ground. I removed both ends and cleaned both battery cables with no improvement. The battery is 1.5 years old and is a gel style from AZ. It happens at all times especially when backing into my garage, even after an extended run on the highway. Any ideas?
Flickering Headlights
- Thread starter LAGA
- Start date
- Status
In the old days that meant alternator..solenoid.. not sure if thats true anymore.
A 2007 vehicle is pretty new , but I don't think it would be out of line to suspect the battery cables could be corroded internally. The headlights on my Jeep were flickering for quite a while and turns out it was an awful connection from the battery to the PDC. Or it could be an alternator or battery problem. What's the voltage at idle when this happens?
Flickering lights is a also common sign of a failed alternator diode.
Last edited:
When they say a ground they most likely mean the ground for the lights.
Anytime I notice anything that is "off" electrically, I really get after the ground side. If your NEG ( - ) post has a clamp style battery cable, I add a soldered lug cable from under the nut to the body nearby. From that same body bolt, I usually add a longer wire/cable with soldered lugs back to the firewall.
On the engine end of the battery ground cable, I add a #8 or larger soldered lug wire/cable up to the actual alternator mount so the regulator actually sees a real relative ground.
With all the mixed metals being used in cars and trucks these days, it's very easy to develop corrosion and oxidation bridges that are really crude semi-conductors with anywhere between 0.2 and 0.5 volt drops across their surfaces. When running the bolts in and out, I always use a modern silicone grease to help slow the creation of these oxidation by-products.
A little tinkering and tweaking the ground side usually greatly improves the vehicles whole electrical performance
As far as the battery cables themselves, if they are crimped ends only (the majority) it pays to actually solder the ends to the cable. If they have corroded or oxidized between the crimp and the wire, you'll need to cut that off, clean the cable, add some tinning fluid and solder on a heavy duty lug. They can be got in large sizes at most truck repair shops for a buck or two.
On the engine end of the battery ground cable, I add a #8 or larger soldered lug wire/cable up to the actual alternator mount so the regulator actually sees a real relative ground.
With all the mixed metals being used in cars and trucks these days, it's very easy to develop corrosion and oxidation bridges that are really crude semi-conductors with anywhere between 0.2 and 0.5 volt drops across their surfaces. When running the bolts in and out, I always use a modern silicone grease to help slow the creation of these oxidation by-products.
A little tinkering and tweaking the ground side usually greatly improves the vehicles whole electrical performance
As far as the battery cables themselves, if they are crimped ends only (the majority) it pays to actually solder the ends to the cable. If they have corroded or oxidized between the crimp and the wire, you'll need to cut that off, clean the cable, add some tinning fluid and solder on a heavy duty lug. They can be got in large sizes at most truck repair shops for a buck or two.
Last edited:
You could temporarily parallel the ground wire from the battery by connecting a jumper cable from the negative of the battery to an unpainted bolt on the vehicles frame and see if the flickering stops while your temporary additional ground is present. If it stops the flickering you need to improve the ground connections of the vehicle, and if it does not stop the flickering your problem is elsewhere.
Last edited:
No HID`s Using a voltmeter Get a reading 0f 440 on the diode setting. There is a AZ a block away and I tested a new alternator and got 460. However, when test at battery for AC current, I get 30 on the lowest AC setting on the meter (200). AZ does not test diode or AC. Parallel ground cable did not help.
Something like that is likely controlled by body control modules and/or DRL modules. The ultimate ground could be inside the cab or somewhere equally strange.
You could also have a bad connection in the ignition switch/BCM/alternator/battery circuit, where the alternator isn't "sensing" properly and the control for it is getting in a feedback loop.
You could also have a bad connection in the ignition switch/BCM/alternator/battery circuit, where the alternator isn't "sensing" properly and the control for it is getting in a feedback loop.
Originally Posted By: eljefino
Something like that is likely controlled by body control modules and/or DRL modules. The ultimate ground could be inside the cab or somewhere equally strange.
You could also have a bad connection in the ignition switch/BCM/alternator/battery circuit, where the alternator isn't "sensing" properly and the control for it is getting in a feedback loop.
How can I diagnose that myself or do I need to take it in? Voltage regulator?
Something like that is likely controlled by body control modules and/or DRL modules. The ultimate ground could be inside the cab or somewhere equally strange.
You could also have a bad connection in the ignition switch/BCM/alternator/battery circuit, where the alternator isn't "sensing" properly and the control for it is getting in a feedback loop.
How can I diagnose that myself or do I need to take it in? Voltage regulator?
Did you check the diodes like in the first video? If you can access the main wire there is no need to remove it from the vehicle.
You could try an add on ground to the light wiring ground wire with a scotchlock connector as a temporary test.
You could try an add on ground to the light wiring ground wire with a scotchlock connector as a temporary test.
Originally Posted By: Trav
Did you check the diodes like in the first video? If you can access the main wire there is no need to remove it from the vehicle.
You could try an add on ground to the light wiring ground wire with a scotchlock connector as a temporary test.
Yes I removed the positive cable, filed contact points on body of alternator and stud.
Did you check the diodes like in the first video? If you can access the main wire there is no need to remove it from the vehicle.
You could try an add on ground to the light wiring ground wire with a scotchlock connector as a temporary test.
Yes I removed the positive cable, filed contact points on body of alternator and stud.
Trav-
in the second video, the meter is set the 200 volt AC position and the meter is indicating almost 30 v AC. Is this even possible? More than 30 ac and the car runs? Digital electronics require absolutely clean DC voltage. That much AC should fry the electronics. Perhaps I'm missing something. Pls explain.
Thank you
in the second video, the meter is set the 200 volt AC position and the meter is indicating almost 30 v AC. Is this even possible? More than 30 ac and the car runs? Digital electronics require absolutely clean DC voltage. That much AC should fry the electronics. Perhaps I'm missing something. Pls explain.
Thank you
AFAIK you really want to see close to zero but anything over .5 VAC is a good sign of bad diode. Now I watch the video closer he has a defective diode, I thought he had .29 not 29.0.
The battery absorbs the AC ripple but that much I would guess as you say could be damaging to the the system.
Alternator test
The battery absorbs the AC ripple but that much I would guess as you say could be damaging to the the system.
Alternator test
Originally Posted By: willbur
Trav-
in the second video, the meter is set the 200 volt AC position and the meter is indicating almost 30 v AC. Is this even possible? More than 30 ac and the car runs? Digital electronics require absolutely clean DC voltage. That much AC should fry the electronics. Perhaps I'm missing something. Pls explain.
Thank you
Just a couple of points.
1. cheap meters are set for the RMS value to be at 60hz. If the freq is not 60hz, the reading isn't true for a cheap meter.
2. all vehicle electronics expect noisy DC, so all modules sensitive to spikes will be well-filtered on the front end. While I'm pretty sure the true value is not that high, or if it is, it's much more "spike" in nature, I am comforting saying they can handle more noise than one would think. Vehicle electrical system is messy power.
-m
Trav-
in the second video, the meter is set the 200 volt AC position and the meter is indicating almost 30 v AC. Is this even possible? More than 30 ac and the car runs? Digital electronics require absolutely clean DC voltage. That much AC should fry the electronics. Perhaps I'm missing something. Pls explain.
Thank you
Just a couple of points.
1. cheap meters are set for the RMS value to be at 60hz. If the freq is not 60hz, the reading isn't true for a cheap meter.
2. all vehicle electronics expect noisy DC, so all modules sensitive to spikes will be well-filtered on the front end. While I'm pretty sure the true value is not that high, or if it is, it's much more "spike" in nature, I am comforting saying they can handle more noise than one would think. Vehicle electrical system is messy power.
-m
- Status
