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The flickering of the headlights and “brights” dash light only happen when the headlights are turned on. No other dash light or interior car light flickers. And there are never any flickers with headlights turned off. I haven’t noticed any performances issues during the flickering. Notably - I just recently flushed all my A/C lines and evaporator and replaced all the components. I was deep into the passenger side dash to remove the blower and ECM to get to the TXV to replace it. Everything works fine. Drove the car daily for 1 week after doing all this car work and the lights never flickered. Just started flickering yesterday.

My research found the following that I will look into:- Battery, battery terminals

- Alternator, make sure alternator plug is pressed in, check connection b/w battery and alternator

- Engine ground wires

- Fuse 15 inside car (alternator speed sensor fuse)

- Wiring harness behind the manifold and 02 sensor wires

- Test voltage regulator?

- Electronic load detector unit

- Ignition switch

- Unplug/plug fuse box connector in engine bay

anyone have other ideas? This seems weird that it only happens when I turn the headlights on? If someone could post useful wiring diagrams that would be super helpful!

edit: flickering is reproducible when my a/c is turned on: Battery is good. Alternator checked at auto zone was good. With the car running I get 14.5V even when I get it up past 2000 rpm. When I turn the A/C on the clutch engages and the voltage across the battery drops down to as low as 12.7V. Then the clutch disengages and the voltage climbs. It continues to cycle like this and when it does this my headlights flicker. It’s the weirdest thing. Any ideas?

 
Rep Power: 366

what are "brights"?!?

 
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the dash light that comes on when you turn your brights on

 
Rep Power: 366

are you talking about high beams?

 
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No led bulbs installed? Bad voltage regulator or alternator would be my guess

 
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yeah I guess we call them brights where I’m from

 
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I thought that too. The alternator checked out good at AutoZone. And my volt meter testing showed that even with accelerating the car, the voltage stayed stable across the battery around 14.5V. I thought that if it was bad voltage regulator then the voltage would continue to climb?

also - I do have high quality LED bulbs. But I’ve had them for a year now and never any issues. It’s also both headlights that flicker not just one.

and I can’t explain why the A/C compressor clutch engages on and off as explained above. I figured it was somehow connected to the headlights issue

 
Rep Power: 222

The compressor is going to cycle on and off.
I'm going to suspect the bulbs although i wouldn't trust anything from autozone

 
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I’ll pull an alternator from a junkyard tomorrow for 25 bucks and see if that fixes my problem. I’ll message again with the results. Thanks for your help!

 
Rep Power: 366

wiring damaged somewhere?

 
Rep Power: 511

is it actual flickering or intermittent dimming?

 
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it’s definitely flickering. I think it might be that since my A/C never worked since I got the car last year, I never turned the A/C on at night to notice the flickering of my LED bulbs. Im looking into buying some decoders for the LEDs now. I’m thinking the compressor just takes a lot of voltage and the voltage drop is messing with the LEDs. I’ll message back when I have them installed and let y’all know if it fixes the problem. Decided to hold off on just replacing the alternator for now.

 
Rep Power: 366

the compressor mostly uses the engine power.
your electrical wiring to turn compressor on is the suspect of drawing electrical power, most likely something is shorting somewhere behind the dash

 
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SOLVED

You were right — it was the bulbs. I purchased:

GTR Lighting - PWM LED/HID Anti-Flicker Decoders - H4/9003

From the same site I got my LED bulbs from last year. It’s really odd to me how it was fine all year and just started happening 1 week after doing A/C work (compressor, condenser, drier, TXV, flushed all the lines). It occasionally happened even with the A/C off. Now there’s no flickering at all.

Thanks everyone for your comments!

 
Rep Power: 511

Something is striking me as odd if it was because of the bulbs (and presumably low voltage being supplied to them). Automotive headlight bulbs typically have an acceptable voltage range of like.. 10-30VDC. If you were experiencing flicker, that tells me voltage was dropping below that acceptable range. You might have fixed the flickering problem with the decoders, but you may have a larger problem at hand. You wouldn't happen to have any voltage readings while the car is operating, would you? Specifically, when any dimming starts to occur.

There is a very real possibility that I'm just thinking worst case scenario

 
Rep Power: 222

Probably just getting worn, i had it happen in my 2000

 
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When flickering with a/c on the voltage was a low of 12.7V across the battery. I thought maybe I had a bad voltage regulator but with acceleration the voltage remained stable at 14.5V. Never higher. So I figured that was good enough diagnosis to rule out regulator issues

 
Rep Power: 511

That's normal operating voltage range. I'm going with that Colin said then. I was just thinking about the time my alternator died on my way home from school back in like.. 2012. I had a voltage gauge in my car (by way of an A'PEXi VAFC-II) and I was limping it home at 11V right as the sun was going down. Wasn't a fun time.