Advice needed: Flickering lights

[S.Hicks]

Did anyone ever get a fix on this, my 09 just started this the other day. My scan gauge and a multimeter both are picking up the alternator output bouncing back and forth between 12 & 13 volt range. All the lights pulse except the HID's (the ballast probably keep those from pulsing). Have not started to isolate components yet, assuming the voltage regulator is going, but hate to spend $$$$ on alternator and still have the problem. thanks,

[TA427]

The best way before throwing parts at it is test for possible voltage drops. First start at the battery on the neg. Side, with the voltmeter, touch black lead of meter to only top center post of batt.then red lead of meter to negative battery terminal.anything over 1 half volt (0.5v) is considered excessive voltage drop although depending on meter 0.7v is ok. Now do the pos side at battery, only using red lead on batt.post only then black lead on positive terminal, these readings there should read 0.2v or less, if not it means terminal to post has hi resistance wich would just need cleaning.now go back to neg side of battery with black lead to neg batt terminal and an extension to cable lead at left side of front underhood ground stud again should be less than 0.5v.with engine off first then again while idling.then back to pos. Side of battery with red meter leads and black leads to underhood red jumper post off first then idling, if that passes, black leads to neg. Underhood jump post, then red lead to alternator metal housing.keep in mind the bcm controls alt output so you would need a scanner that reads bcm data, if the bcm field command is steady most likely the alt. for sure .unless bcm has volt drop to its grounds or ign and batt leads which is rare, but then you do the same to its leads for + and -.welcome to my world in a gm dealer ! Remember diagnosing is 80 % of the repair, get some help doing this and take your time, let us know

[Napalm]

since getting a cam in my car I notice my interior lights do this a bit at idle and I think it has a lot do to do with the swings in the RPM causing the alternator to pulse the load. I think over time the computer might well have compensated for it a bit. As it's no where near as noticeable.

But I think a weak alternator voltage regulator makes the problem worse.

[RichsGreyGT]

since getting a cam in my car I notice my interior lights do this a bit at idle and I think it has a lot do to do with the swings in the RPM causing the alternator to pulse the load. I think over time the computer might well have compensated for it a bit. As it's no where near as noticeable.

But I think a weak alternator voltage regulator makes the problem worse.

I had my alternator checked back in the winter at an Advance Auto and guy said the voltages were fine with his meter. I've been driving the car alot this spring and lights dim continuously at dusk/night.

Its very irritating. Its been doing this since 2011. Luckily I don't daily drive the car.

if anybody has any more ideas/thoughts, I'd be very happy to hear.

[TA427]

Where did he check it at which posts ? First is at the battery then the posts under the hood also you must simulate the conditions while checking, car in drive, in gear foot on brake,lights on, AC on etc.

[Napalm]

do you have a meter to check your self? becasue I would do it myself to know for certain.

1) volts on battery - car off - at the terminals on the battery.
2) volts on battery - car off - at the end of the metal stubs holding the battery cables - or that top nut on the cable. (difference should be less than 0.5V
3) volts on battery cables - car on at idle Should come up to 13-14.6 or so.
4) volts on battery terminals - same as 3.
5) volts on battery terminals - car on, at idle, ac on, headlights on, radio on. - might go up a tick but shouldn't go down - again in that 13 to 14.6 range still.
6 Volts AC - at battery terminals - same condition at 5. meter reading AC volts and zeroed out per meter manual - should be under 0.5 and ideally .1-0 but I think that's rare today.

AC volts kills your battery. even agm ones.

[RichsGreyGT]

Digging up this old thread I started....

I ended up taking my car to a local tuner to tweek my tune and dial in the A/F ratio a few months ago. After he tuned, my flickering lights seemed to have gone away.

I would have bet money it was electrical/mechanical not in the tune. If it comes back, I will update again but glad its gone for now. People always thought I was flashing them and they would hit me with bright lights about 1/3 of the the time.

[WarnerUnjuh]

Small update on this - lights are still on after a short drive. Could just need re-set though.

Going to try changing the relays and see if they are the fault. Still a bit miffed