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Real Subwoofer Install on 2023 Model 3

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Hi! I’m new here and I have just completed an install of an old Rockford Fosgate P3001 monoblock and a Rockford 10” P2 subwoofer in my 2023 Model 3 RWD (15.5V system). I’m happy to say it’s all working perfectly!

This install method (scraped from various forum posts and a week of research) should allow you to install ANY average amp in this car, as long as the wattage isn’t insanely high. I’ve attached links to the gear I used. These are *not* affiliate links, I legit just want to help the next person.

Here’s my circuit design:

sub-v2.png


To adapt the voltage, I’m using a rectifier that was designed for solar applications. In the diagram, this looks like two diodes at the top left.

By using the two appropriate terminals, it will induce a voltage drop of ~2V, dissipating a small amount of power as heat. This is why the rectifier is attached to a huge heat sink (I like overkill).

There’s a diagram on the side of the rectifier, but in my case, I connected the positive wire from the penthouse into the connection marked as negative on the rectifier. Then I hooked the positive on the rectifier into the rest of my circuit. This causes the power to pass through two diodes, inducing the desired voltage drop.

To fix the inrush current (and avoid getting errors on the computer), I’m using a 300 watt 5 ohm resistor. This resistor is connected across the switched legs of a 40A automotive relay (Novita RL44). When the relay is open, the energy flows through the resistor. When it’s closed, the resistor is bypassed.

***Important note about electromechanical relays***… when they shut off, the magnetic field collapses and generates a spike of voltage which can go back to whichever device is hooked up to the coil. To solve this, I have added a 1N4007 flyback diode across the relay coil. You must make sure the striped end of the diode is on the positive side of the coil. I crimped it into the relay harness, seen below.

IMG_6318.jpeg


To get the remote signal, I got an accessory power harness that attaches to the OBD connector underneath the rear vents. In this harness, the red wire is the switched accessory power and the yellow wire is constant 15.5V. I hooked this all into a Crydom 3A DC-DC solid state relay so that when the accessory power is on, it bridges the yellow 15.5V to a wire running to the remote input of my NVX XLCA2.

Here’s a picture of the total setup under my trunk:

IMG_6356.jpeg


To get the audio signal, I tapped the left and right woofer wires on a Hansshow harness.

I hope this helps someone!
 
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Hey there, I've followed yours and thesufferings guide on my 2023 RWD, but I'm still getting all kinds of PCS/BMS faults (VCFRONT_a192, VCFRONT_a129_pCsEFuseTrip).

I've got a 200a NVX mech relay/battery isolator and a 200w 4ohm resistor bridging the relay terminals. I've also ordered a 300 watt 5ohm resistor like yours.

I'm just curious whats the wattage of your amp? And what is the final voltage/current going through your resistor? On my end it seems very low like less than 1v, and the amp/LOC never even lights up :( so my theory is the caps are not getting charged and I'm still getting an in rush current when the remote signal comes on.
 
Damn, if you had sent this yesterday, I would be able to check. I’m out of town right now but I have set a reminder so that when I get home on Monday, I will test the voltage through the resistor.

Yeah, that other post you mentioned was a HUGE help to me when I was trying to figure this out.

My amp is an old Rockford Fosgate p3001, 300W RMS.

If it’s hooked up as described, the resistor should essentially be bypassed when the remote signal comes on so I’m wondering if you’re not getting a remote signal? I feel like the amp should turn on.

Where is your remote signal coming from? From what I understand, those battery isolators use more current than a standard relay. Also, I’m guessing it could also benefit from a diode to prevent the fly back on the coil.

Any pics of how you’ve got things wired up?
 
IMG_6456.jpeg

Also, my solid state relay wired in differently from the one in that other post. Not sure if it makes a difference, but I put the higher current input wire to the top left. Negative and control wires in the bottom. Top right is the remote signal output on mine. My remote signal is coming from underneath the rear vents as opposed to the left kick panel because I found a nice little harness to do that without having to splice factory wires. Apparently Tesla recommends using the output from that OBD system for driving accessories.

You could try testing your remote signal output with a multimeter just to ensure it’s actually working.

I can’t seem to find any info about that particular error code.. Unsure if it means too much draw on the penthouse or if it’s complaining about the current drawn by your relay/battery isolator.
 
Looking to install a sub/amp in my 21 Model 3 Long Range... All this extra stuff compared to an ICE car install is making me nervous, lol.
Oh for sure it’s a bit more involved than a regular car. However, there are only two challenges you wouldn’t experience with an ICE car:
  1. The computer can get upset by large sudden current draw on start-up
  2. The voltage on the newer models is sitting at 16V or so (dunno why I wrote 15.5 above, I must have read it somewhere), so a higher voltage than most amps want.
Otherwise, on most any vehicle, you’d still have to get a remote signal from somewhere and you’d still have to tap woofers somehow.

Either of those could be easier or harder in any other vehicle.

Once I realized that, I wasn’t afraid of it. But it’s definitely not plug and play.

I saw one guy on YouTube who added a basic Kicker sub with an integrated amp and he says it worked just fine at the 16V, directly wired into the penthouse.

But I couldn’t find that model for a decent price and my coworker sold me this Rockford sub and amp for $100, so this is how I got into this madness 🤣