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97 F-250 HD
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Discussion Starter · #1 · (Edited)
Here's how to stop flickering on interior lights on a per-light basis, no matter how bad your power draw is, even if an anti-flicker harness on the circuit won't work.
This also has the effect that when you turn the light off that it will fade out over a few seconds instead of quickly blink off, so it saves stress on the LED's and they will last longer.

Shortly: Why would your LED's flicker at all?
-Powerful stereo
-MPPT charger on the battery system
-Other aftermarket electronics
Well this will fix that. Even if putting a single anti-flicker harness on the circuit doesn't, doing this to each light will.

For interior LED's use a diode in series, capacitor and resistor in parallel after it to stop flashing.
(using these parts you can do 100's for the cost of a single pre-made unit)
Resistors: 220 ohm metal film fixed
Diodes: 100V 3A diode
Capacitor: 2200 uf electrolytic
❄NOTE that if you are in a cold environment (14 F or colder) you won't want to use this type of capacitor, it could stop working.
(there will be updates in place of this text if this turns out to be a problem)
https://www.amazon.com/gp/product/B07QK9ZBVZ
https://www.amazon.com/gp/product/B07SC4G7Q6
https://www.amazon.com/gp/product/B07YYLX3GQ

The right way: Disconnect and insulate the negative battery cables.
What I did: Do it under load because I am lazy, accidentally short it and end up replacing the fuse.
At least you should: Look in the fuse panel and pull the fuse for the dome/interior lights first
Striped wire is the positive wire.
You can unbutton the clip that holds the door light wire so it will come further past the door cover.
Cut, strip, twist, solder, insulate, as pictured, or better if you care more.
If you wanted to get crazy you have the diodes to add a bridge rectifier.

Here's what I did in pics and it works great. Make sure you tape it up or use heat shrink.

159402
159403
159404

159405
159406


159407
 

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97 F-250 HD
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Discussion Starter · #2 ·
Finalized this thread for interior lights with instructions and pics. Will create another one later, for the brake light resistor.
 

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That's pretty scary...

What do you think this is doing? The diode in series drops the voltage to the LED by ~0.7V, and makes the capacitor work only on that one LED. The capacitor keeps the LED lit slightly longer and makes it dim as it goes out; but it has NO effect on the LED's durability. The resistor does almost nothing.

This shows an easy way to keep the transmission, cruise, & ABS working if all of the brake bulbs are swapped to LED:

(click this text)
 

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Why not just fix the intermittent power? All of the LEDs in my trucks work smoothly without any capacitors or hacking.
 

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Discussion Starter · #6 · (Edited)
Why not just fix the intermittent power? All of the LEDs in my trucks work smoothly without any capacitors or hacking.
In some cases the fix is extreme, like in the case of oversized stereo systems, you'd have to add a very large capacitor just to stop the lights from pulsing/dimming/flickering.

In some cases there's just nothing you can do, such as if you have a pulsed charger on the system like a solar MPPT controller. If the truck system is low and being charged then the lights will pulse.

This kind of arrangement is really common in (decent) boombox stereos, where you will find this between a speaker and tweeter on the same hot (no resistor) so that the tweeter doesn't power dive when the speaker sucks more amps. It can be used for a very wide variety of things where you want to smooth out power on a DC endpoint.
 

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In some cases the fix is extreme, like in the case of oversized stereo systems, you'd have to add a very large capacitor just to stop the lights from pulsing/dimming/flickering.
If a large amp is causing the truck's voltage to drop, either the amp is too large for the battery, or there are wiring problems between the battery & amp. Hacking the light wiring will not fix either of those. That would be a band-aid.
In some cases there's just nothing you can do, such as if you have a pulsed charger on the system like a solar MPPT controller. If the truck system is low and being charged then the lights will pulse.
If the charger is putting out irregular voltage, hacking the light wiring will not fix it. That would be a band-aid.
...in (decent) boombox stereos, where you will find this between a speaker and tweeter on the same hot...
It doesn't sound like you understand how speakers or audio filters work. Decent stereos have crossovers between speakers of different frequency ranges.

In any case: none of the lights on my trucks flicker; and if they did, I wouldn't hack their wiring the way you described. I'd fix the root of the problem. Drive on.
 

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Discussion Starter · #8 ·
If a large amp is causing the truck's voltage to drop, either the amp is too large for the battery, or there are wiring problems between the battery & amp. Hacking the light wiring will not fix either of those. That would be a band-aid.If the charger is putting out irregular voltage, hacking the light wiring will not fix it. That would be a band-aid.It doesn't sound like you understand how speakers or audio filters work. Decent stereos have crossovers between speakers of different frequency ranges.

In any case: none of the lights on my trucks flicker; and if they did, I wouldn't hack their wiring the way you described. I'd fix the root of the problem. Drive on.
Not sure what reason you have to question this at all. It performs as stated. This isn't about overhauling an entire power system, which most people aren't skilled enough to even begin to attempt, it's about how to stop a light from flickering, which I don't know why you think that is uncommon. It's super common.
 
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