5th Gen 4Runner - Auxiliary Wiring Schematic

[PJSnow]

Hello all. I'm new to this forum and also relatively new to all things electrical. My understanding is fairly basic but I have been trying to self educate myself as best possible.
I am currently working on organizing the wiring for my auxiliary lighting on my 2018 4Runner and I have put together a schematic to summarize my ideas. There are a couple things I would like to achieve:
1. Organize all the wires in the engine bay and behind the dash. Currently it is a mess of various individual relay harnesses that came with lighting kits (each having their own battery connections). I have come a long way since I started this electrical journey and I now have the proper skills and tools to crimp connections and properly size wires.
2. Maintain a factory/OEM look without splicing into factory wiring or disturbing any of the original systems. So far I have been able to do this by using fuse taps and factory connector harnesses.
3. Be able to trigger my auxiliary lights with a flick of the steering wheel stalk (high beam trigger) AND individually with their own switches. This has been the more challenging aspect of this project and what I am mainly looking for input on (double relay solution presented in wiring schematic).

Apologies for the lengthy first post but hopefully this gets all the info across. Feel free to skip to my schematic but I appreciate any help, guidance, suggestions, or other. Thank you in advance!

Background
The 5th generation 4Runner has a combined Daytime Running Light (DRL) and high beam circuit which powers a halogen bulb. Toyota decided to use the full 12 volts to trigger the high beams and they reduce the voltage to about 9.6 volts to run the DRL with a PWM (pulse width modulation) signal. I am very new to PWM and I have no way to test/detect it. I understand PWM pulses an electrical current very quickly to limit the brightness of the bulb. Most owners decide to switch out the halogen bulbs for LEDs and report flickering when in DRL mode. I was able to find a set of LED bulbs that include a module/driver to eliminate the flickering (no idea how that works).
Over on the 4Runner forums, a member started a thread on filtering the PWM to use the high beam trigger (here is a link to that thread if anyone is interest). The issue they encountered was a flickering/rattling relay from the PWM signal. The original poster has moved on to other projects but he provided some good info, one of which lead me to this forum (https://www.electro-tech-online.com/threads/filtering-pwm-on-12v-circuit.128439/). This was a very helpful thread and I hope to implement the PWM filter if necessary. Unfortunately, I have not personally experienced the PWM signal and when testing an automotive relay, it did not flicker for me. But I noticed the relay was triggered for both the 12V high beam voltage and the 9.6V DRL voltage, meaning I could not simply tap into the high beam circuit for a signal.

Current Solution
I found a Reddit post discussing the high beam circuit which lead me to a low voltage cutoff module. I did not like the idea of the voltage display on that specific module, draining my battery (high beam fuse reads 0.05V even when the vehicle is off), therefore I found one without a display. I ordered one up and it seems to activate when the high beams are triggered and is off when the DRLs are on. I think the voltage trigger issue is solved but I'm not sure if the PWM will give me issues. The last thing I want is for the pulses to rattle the module or my other relays and reduce their lifespan or worse (can it damage the system?). I have incorporated the low current module into my wiring schematic but I'm not sure if the PWM filter is needed, where it would be needed (before/after the module), or how to wire it up. I plan to use a project box to house the module and maybe I can fit the filter along with it, depending on the assembly.

Questions
That brings me to a few questions. Now that I have convinced myself with a wiring schematic that this is feasible, I wanted to get a second set of eyes to give me feedback. I also have a few questions/concerns that stem from my lack of knowledge on electrical systems.
1. I drew up the PWM filter connected to the high beam fuse (with a fuse tap) and before the low voltage cutoff module. Is this the correct location? Is it acceptable to use the same ground for the filter and the module?
2. I am fairly confident in my crimping abilities but soldering is still relatively new/difficult. I understand the filter components (diode and capacitor) should be soldered to the system. Can these be soldered to automotive stranded wire? Is there a way to get a reliable crimp connection? Does anyone have any exampled of these components in a real world application (as opposed to a pcb board)?
3. My double relay solution should allow me to use the high beam trigger to operate my auxiliary lights with the high beams or independently. Both relays will provide power to the individual lighting switches through a single wire ("Y" connection at the wires). I drew in diodes right before the "Y" splice to prevent backflow of electricity. Are these needed? I don't think the relays will ever be running power at the same time, but I'm not sure how the system would react if the diodes were not there. This is definitely an issue with my lack of knowledge on electrical systems and components but hopefully a simple question for someone here.
4. A general sanity check. Does this system make sense? Are there any aspects I am neglecting or overlooking? Any other suggestions or ideas I should consider?

Again, I apologize for the long winded post but I think this summarizes my project and hopefully gives enough information for you all to provide feedback and answers. Let me know if there is anything I forgot to include. And now onto some pictures/diagrams:

Here is an image of my schematic diagram. It is a bit lower resolution but I bubbled the question areas in green for visual identification. I am also attaching a PDF of the diagram (in its original color glory) which should be a higher resolution. Note, this was not created with an electrical software, but instead with a PDF editor that I have handy. Please excuse my lack of drafting abilities. Hopefully it portrays my ideas. (note: the wire crosses are indicated with double ovals and the "T" connections are indicated with a circle/dot)

 

[rjenkinsgb]

Hi,
pretty good diagram for a first attempt!

Just for info, "flow" is normall left to right when possible, and non-connected wires simply cross over. Junctions at a a T or cross have a solid "dot" or blob to represent the connection.

However yours is perfectly clear as it is.


If use a large wire ended diode, eg. 3A or 5A rating, the leads will be quite thick and you should be able to use a red butt splice to join to the vehicle wire, then add hi-shrink adhesive lined heatshrink over the whole thing to seal it.

The capacitor is a bit trickier, as it will have thin lead. You should still be able to crimp them though, but fold them to give hopefully four thicknesses of the thin wire within the crimp?

I'd then add similar heatshrink over each lead individually, and a larger version over the whole assembly to prevent any vibration between the wires and cap body, that could crack the wires.


Re. crimping, be sure to only use a compound action tool similar to the image below, that has "U" jaws to prevent the crimps just flattening & spreading sideways. That happens with the basic plier type tools in many DIY crimp kits, which can lead to very poor and unreliable connections.


An electrical crimp must provide enough force so the metal is compressed and flows to some extent, so it has good contact areas and the force between the parts excludes air (oxygen) so it cannot tarnish or corrode over time. Technically, a "gastight" connection.

That's one of the reasons it's so important to try and fill the metal section of the crimp (eg. folding thinner wires) with copper before crimping, to guarantee adequate force is created for a reliable connection.

 

[PJSnow]

Thank you for the feedback! It all makes sense and I'm glad the schematic is understandable.

Crimping the diodes and capacitor will certainly make my life easier. I have a Wirefy crimping set and various heat shrink connectors that have worked well so far on other projects, and it seems will work for this project.

Any insight on the PWM filter or the other diodes in my schematic? Or any other general comments on my plan?

 

[rjenkinsgb]

That tool looks good, as long as you don't use the squashing jaws shown fitted in the photo!

I don't think you need the two diodes to the right of the relays; it does not appear either can feed back through the other to do anything.


Looking again, you don't need diodes at all.....

For the filter, you really want a power resistor feeding the capacitor, rather than a diode.
Probably a 1000 or 2200uF, 25V or higher capacitor.

I'd guess at a 22 Ohm resistor may work. I'd use a metal case one rated more than 10W.

That will average out the PWM voltage; a diode would pass the peak voltage regardless of duty cycle - OK if you wanted a clean switch-on regardless of duty, but not for the low voltage cutout relay.

The resistor has to be quite low, as that's also driving the next relay once the voltage is adequate.

 

[PJSnow]

Noted on the diodes. My understanding of the filter is primarily the previous post from 2012: https://www.electro-tech-online.com/threads/filtering-pwm-on-12v-circuit.128439/post-1069375
Trying to understand how the components work together, I assume the capacitor stores energy and releases it slowly to maintain a constant voltage (eliminate/even-out the PWM signal). Does adding a resistor shed off some energy? Would that slow down the time for the capacitor to charge up? Doesn't the capacitor discharge at the same voltage regardless?

The capacitance values you suggested are much higher than what was proposed in the previous thread I linked. It mentions the larger capacitance would increase the time it takes to de-energize. Being that this is for a high beam trigger, I expect there should be minimal delay (example flashing high beams quickly or turning off the high beams to not blind oncoming traffic). But maybe swapping the diode for a resistor requires a higher rated capacitor?

Again, I apologize for my limited knowledge on the subject but I appreciate you helping me out!

 

[PJSnow]

I did more research to understand PWM signals better and came across an interesting article. I certainly understand it more and it clarified the RC filter functionality.

It seems I would need to better understand the frequency of the 4Runner's specific PWM signal before I can accurately size the resistor/capacitor. I assume the only way to do that is with an oscilloscope (which I do not own). Or maybe I could use trial and error, but I'm not sure what to test on because the low voltage cutoff module I purchased does not appear to flicker. If I understand the RC filter correctly, I may not even need the low voltage cutoff because the filter should provide the correct voltage trigger when the high beams are activated.

I may try to run the low voltage cutoff module without the RC filter since the one I purchased does not seem impacted by the PWM and it is simply triggering another relay. I can't see another way to accurately find the required resistor/capacitor size to quickly trigger my auxiliary lights when the high beams are triggered and to turn them off quickly when the high beams are turned off.

 

[rjenkinsgb]

I believe the idea is to trigger on main beam, but not the PWM-dimmed running lights?

There should be no PWM while the main beam is on, so as long as the low voltage relay is not triggering or rattling when on running lights, you probably don't need a filter.


Re. the filter - during each PWM cycle, the series resistor partly charges the cap while power is on, then partly discharges it while power is off (and the lamps are pulling the voltage down).

The result is something like this, with the voltage jittering around the average on/off ratio.
The amount of jitter depends on the frequency and R C values.

(Ignore the voltage and time, that's actually for a high frequency logic signal - but the effect is the same).

 

[PJSnow]

I see, so the resistor is essentially "doing work in both directions" to maintain the average voltage. It seems to be a very simple concept but effective.

From my quick testing, the low voltage module/relay is not triggered with the PWM and does engage with the full voltage (high beams on). I will try to install it alone for now and may post back here if I experience flickering. Thank you for the help!