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Stock amp power for aftermarket amp turn-on?

Discussion in 'Model 3: User Interface' started by corndog, Jul 16, 2020.

  1. corndog

    corndog Member

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    Working through my Model 3 Premium audio upgrade. There is a lot of discussion/advice about where to get your turn-on signal for your after market amp, but I'm not sold on running a line all the way from the front of the car (VC left or cigarette socket). I haven't seen anyone mention using the red wire that powers the existing rear amp. I've tested that it turns on 4-5s after the big battery, which seems ideal. And it's so conveniently located.

    Is there any reason people aren't / I shouldn't use this as the signal to switch my power relay?

    M3S-TandL-TravisPinout-768x272_edit.png
     
  2. adrianp89

    adrianp89 Member

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    It's 15v so I def wouldn't use it directly to the amp. 15v may be too much for a relay but never tried, I would also step down the voltage is 12v. As little time as it takes to run a wire to the front of the car - I would just do it the right way the first time.
     
  3. corndog

    corndog Member

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    All the "12v" circuits in the Model 3 are 14-15v. It's actually very common for 12v circuits to be higher than 12v. The amp is good for 9-16v and the relay is good for 4-32v, so the voltage is definitely not the problem here. I'm wondering more about the behaviour of the line or whether it has some characteristic that makes it unsuitable.

    There is no "right" way. This is all just figured out by people doing aftermarket mods. Just because the first guy did it one way, doesn't mean its the only or "right" way to do it.
     
  4. Idkorcare

    Idkorcare Member

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    I dont have premium but id assume it wasnt used due to staying on whenever the car was awake so id check for when it shuts off.
     
  5. adrianp89

    adrianp89 Member

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    12v circuits and 15v usualy don't mix. Anything over 14.4 and you are overcharging. Is amp remote input rated to 15v? I highly highly doubt that. I am curious on the amp - not many can run on just 9v, and some can run higher voltage but are usually designed specifically for that. Same for the relay - your standard SPDT relay usually needs at least 10v to trigger, and again pushing over 14.4 is going to burn the coils.

    Anyways - if you want to check the "behavior" of the line - do it the old fashioned way, with a DMM. Run the car/stereo in different ways and see how voltage re-acts. If you have concerns with it back-feeding just diode isolate it.

    Another option is to see if your amp has hi-level inputs and auto-turn on. This would be the easiest solution.

    There is a right way and a wrong way to grab a remote lead. I've been professionally installing for 15 years now. I've had plenty of tricky instances with finding a remote wire.

    In case you feel like running some wire - here are some note from our installer database:

    "Vehicle overview

    Switched power can be found in driver kick thick Light Blue or at Cig Lighter in center console. To gain access, remove trim panel above it.
    Pull side panels directly outwards to remove.

    **Note** if vehicle has had firmware updated to allow sentry mode these wires are now constant with no way to switch in vehicle settings. Found White wire in driver kick plug that goes to driver door twisted pair with a blue wire. Used to trigger a relay and used light blue in conduit as constant (sentry mode)

    If installing an amp use battery under hood. Do Not Use DC to DC converter under rear seat. Grommet on drivers side firewall is more open in the vehicle. Passenger side has many large power wires running through and wouldn't recommend using."

    According to the notes there is also a 12 gauge wire solid red wire in the passenger kick that provides 12v when the brake is pressed to engage the car.(Not sure if I would use that one though)
     
  6. corndog

    corndog Member

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    I'd have to check again, but I'm pretty sure the line is actually less than 15v. I measured 14+, but not sure exact value.

    Yes, this is what I'm doing. The switched signal will only activate the relay, which, as I said before, is rated for 4-32VDC control voltage. (it's allowable load voltage is 0-30VDC).

    As per it's specs, the amplifier (Alpine S-A60M) has an allowable 9-16v.

    It looks like your installer database is out of date. These cars got sentry mode ages ago, so it's advice on which wires to use is no longer valid. And it's advice to use the 12v battery instead of the DC-DC converter is wrong by every account I've read. It's well documented that using the 12v battery causes errors/alerts and can lead to premature battery failure.

    A picture is worth a thousand words. Building from Travis Llado's work, this is the plan.

    charging circuit schematic.jpg
     
  7. corndog

    corndog Member

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    I've confirmed that it turns on about 5s after the HV battery power on, and turns off some time (like a minute or something) before the HV battery powers off. It sounds ideal, but I'm just trying to find out if there is any unexpected reason that it's not actually suitable.
     
  8. adrianp89

    adrianp89 Member

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    Very well could be wrong, some guys are idiots that put stuff up there lol but it is also vetted by Master Techs. I’ve yet to do a amp install on a Tesla so cant speak from experience. Three model years in and no service calls for errors based on that info... I’d have to do some more research there before I dove into one.

    At this point no need for a relay, power/ground and grab the high signal, should be a quick install.

    I would just be sure voltage is under 15v. I’ve installed probably a few hundred of the previous versions of that amplifier. Doubt much has changed but it definitely goes into protect we’ll before 9v, wouldn’t trust it over mid 14s. I’m either case that shouldn’t really be an issue. Good luck and enjoy.
     
  9. Idkorcare

    Idkorcare Member

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    It’s probably going to stay on longer than you want when the battery is cooling, charging, or sentry mode for example.
     
  10. Idkorcare

    Idkorcare Member

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    The DC-DC charges the whole car including the 12v battery sometimes as high as 14.7v but normally sits around 13.8-14v.

    Also using the battery for power is a bad idea. The DC-DC converter charges the battery but power is routed from DC-DC to VCRight to VCFront to 12v. If enough current is pulled directly off the battery it stops receiving charge and starts draining the 12v battery.
    If that battery gets low enough the car thinks its bad and makes no attempts at charging until you get the voltage back up high enough and possibly do a hard reset to clear the warning. I put 2 voltage gauges in my car when I did the system, one off the DC converter and one off the 12v batt otherwise I wouldnt have notices it.

    I also professionally installed for about 12 years. I first ran power off the DC converter and didnt like the idea so went back and power off the battery to find that issue so now km back to running off the DC converter.
     
    • Informative x 1
  11. corndog

    corndog Member

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    This only impacts whether my amp will have power available to it, not whether it's turned on/off. The on/off is automatic from the high level speaker signal. I just need the "delay on" to my power relay, after my amp has charged via the resistor first.
     
  12. Idkorcare

    Idkorcare Member

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    I see what your asking now.
    Even if no audio is coming out of the stock amps they are probably on whenever the car is awake, your aftermarket amp will detect the white noise/ power as if they are playing and stay on. I had this issue trying find a solve after they changed VCLeft power.

    Does that make sense? I know the front ICE amp is on when the car is awake, pretty sure the back Amp is pointlessly on as well not to mention its something that could change later, thats why im triggering off the Center console lighting.
     
  13. corndog

    corndog Member

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    Yeah I get what you're saying. I suppose the potential issue is (if my new amp stays on due to speaker signal noise) that I'll get a little more phantom drain with sentry mode on...? Presumably that's fairly minor anyway, and unlikely to bother me much.

    doesn't that only turn on when you open the center console?
     

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