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And also im theory if it was at the battery then wouldn't I also see my dash lights or anything else inside dim at the same time?

Okay cool! All great info. Ill report back in a couple of weeks! Gonna do the LED and if that doesnt work try the harness!

More or less, yes. What matters is where the voltage drop is occurring. If the voltage drop is only at the fuse box itself due to an undersized feed, but the battery is maintaining ~14 volts the entire time, then moving the lights to run directly off the battery will have a positive effect, since they will no longer be subject to the drops affecting the fuse box. However, if the voltage drop is due to the PCM briefly turning off the alternator, or the alternator not yet having caught up to the demand, that drop will be at the battery itself, so it effects everything in the vehicle. Moving the lights directly to the battery wouldn't have an effect there, since they would still be affected by the same drop. In the first video it occurred in conjunction with the AC compressor turning on, which I call normal operation for these cars. My 2000 Regal did that and my parents 97 Lumina always did the same thing. The 2nd video was harder to tell, but it seemingly always happening around the same speed when coasting down makes me think that's when the car is coming out of it's deceleration fuel cut off, and the alternator output is briefly being cut to make the transition back to the IAC smoother. Older vehicles didn't experience this in the same manner, as the alternators weren't controlled by the PCM. Newer vehicles with electronic throttle bodies don't seem to experience this either as the PCM has full control over the throttle itself. I really don't think there is an issue that needs solving. If you want to keep the headlights from showing the effects, you could look at switching to LEDs. The LED chips typically run at less than 12 volts, so they have a voltage regulator to keep things in check. This would prevent them from dimming whenever the vehicle voltage fluctuates slightly. Also, ignore what I was mentioning earlier about the ABS. The ABS kicking in will cause the lights to dim briefly due to the load, but after seeing the driving video, i don't think that's what's happening here.

@Black92GS those harnesses make it to where it plugs poeer straight from the battery rather than the fuse box. In theory if its hooked up like that it should not see a dip since the power wont have to go through the alternator first, right? Or am I mistaken

Okay sounds good, all of that makes sense! I am going to do the LED bulbs and im looking at a relay kit on ebay! I will update in a few weeks to see if I've gotten any better results.. thank you both for your time and insight. You guys have helped a lot!

I don't think that would make a difference here. It's not a headlight specific issue, it's the overall system voltage dropping momentarily and noticeably affecting incandescent/halogen light output and the audible tone from the blower. You can sort of duplicate it by leaving the lights on when you shut the car off. There is a slight but noticeable dim that takes place as the overall voltage drops from ~14 volts to ~12 volts.

Maybe you'll want to look into something like this: https://www.summitracing.com/search/part-type/headlight-conversion-harnesses/product-line/united-pacific-headlight-relay-harness-kits

I don't believe you have an issue that warrants any concern if i'm being honest. I couldn't see the dimming, but I did hear when it took place. What I think is happening there is this: As you're coasting down, the engine cuts fuel and is freewheeling. Once you drop below to a certain speed/RPM, it will switch back to feeding fuel and to the IAC for idle speed control. The PCM is likely cutting the alternator output momentarily at the same time to make the overall transition smoother and to prevent stalling, but this will also result in a drop from charging voltage to battery voltage and then back. Non PCM controlled alternators monitor the voltage and self regulate based on that. PCM controlled alternators have the PCM monitor the voltage and the draw, and can adjust the alternator output as required. It also means they can reduce or cut the output completely in certain states to prevent other issues. If the alternator output is completely cut momentarily, you will immediately drop from charging voltage to battery voltage and then back once the alternator ramps back up. Halogen lighting output and blower speed will change along with this voltage change.

Between the 6 and 7 seconds in this video you can see it if you zoom in. Unfortunately lots of light pollution from the other cars so kind of hard to spot 20251218_182451.mp4

Okay 10-4. After I looked into i saw they were different fuse boxes anyways. So last night took the car for a drive and the wheel speed sensors are all reporting accurately from what we could see. I had a friend monitor while I drive. And of course she didnt wanna actually pulse a whole lot so I couldn't catch a video. I am probably getting some black headlights with LEDs for Christmas.... maybe the LEDs will be the fix since they dont need as much power lol. I am also planning on adding a ground from the engine to the chassis so we shall see. If it still does it after all that im sure ill be back picking your brain thanks again for all fhe great info guys

Nope. As long as it's all tight and clean it should be OK. The loose aux post was more of an issue on the 1st Gen cars. Those used a brass post and nuts that were very easily stripped out and could cause issues.

Yeah I cant see a second one on the box and the top post appears to be fine. Its definitely zinc though, do you think a brass replacement would do anything?

That's the one. It looks like you took care of it with your wiring upgrade though.

Okay I will look into it! And are you referring to the post that is on the top of the under hood fuse box? The pics in the forum thats what it looks like. Not the positive battery terminal itself right?

Check how hot the auxillary battery terminal gets...mine would get hot and cause voltage drops until I replaced it...previous owners thought it was just going through alternators. I had one of the zinc ones (and one with the bottom threads stripped so it was had a couple of washers for spacers and what appeared to be a Delco radio post nut as well) and replaced it with brass...common issue on the B bodies too, and it's the same process and part number for replacement. Might not apply on a 2000, though... Replacing the Auxiliary Battery Post | Page 3 | Chevy Impala SS Forum

Please do. That slight voltage sag (dimming/fan speed drop) that took place above when the AC compressor kicked in is 100% normal operation for these cars in my view, and its just a byproduct of how the charging system is programmed to function. It can happen whenever a large electrical load comes on line at low RPM, and It is definitely visible in the headlights when they are on. My 2000 Regal did this all the time, and the factory alternator and the 6 year old battery were still fully functional when I got rid of that car in early 2015.

Okay 10-4, gonna try and get a video of the lights doing it tonight so you can see!

I will warm it up later today and check the temp of the tubes again.

I'm going to be honest, I don't see an issue there. It cranked just fine, and the dip sounded like the AC compressor kicking on. The slight electrical dip is likely just a product of a slight lag between a large electrical load kicking in and the duty cycle of the alternator being increased adequately to compensate.

Hey man I know this is super late reply so you may not even see this, but where did you get the puddle lamps? And were they plug and play or did you have to fab anything to get it mounted?

Good morning! So last night I took out the ABS fuse while I eas driving around. Unfortunately the headlights would still do the same thing I am still going to look into the sensors today as I do have a random grinding sound that will come and go from the rear, so maybe a bad wheel bearing. That being said do you think its something else since it still did it with the fuse out? I am also attaching a video of what the interior lights do at first start up. The noise and the way the lights act are very similar to the what the headlights do when slowing down. I had my park brake on this morning so didnt check the headlights unfortunately. Thanks in advance for the help, im still new to electrical so excuse my ignorance on next steps! 20251218_072241.mp4

Seems unlikely that it would air-lock and then work properly, then air-lock again. Same with plugging the coolant flow path--I can only think of one thing that would plug the heater core sometimes, and not other times. So I'm at a total loss as to why both heater hoses are not "hot" whenever the engine is fully-warm, unless you have a faulty heater-control valve, or heater valve control mechanism--dash controllers, faulty vacuum hoses, etc.

Man thank you so much for all the info! Going to dive into this tonight and see what I find. Ill post tomorrow with the results

You don’t have to. I did because I was I was too cheap to fix it properly at the time. No ABS was far safer than unwanted activation. Sometimes, there is a bit of rust scale that builds up and lifts the sensor (rust jacking), changing the air gap and making the signal weaker and less reliable. Other times, the wheel hub begins to wear internally and can cover the sensor with metal filings, making the signal weaker. The sensors themselves can also go bad. If your scanner is Bidirectional, then the odds of it being able to read ABS data is pretty good.

Ah dang, so you just run without ABS then? My scanner is bi directional so I am going to try and drive it later maybe pin point a bad wheel speed sensor