SOLVED: I'm Stumped: aftermarket subwoofer only works if key isn't in the car.

[Ride_the_lightning]

TLDR: my Kicker sub works if the key fob isn't in the car. Carscanner revealed that my 12V battery voltage is 14.5V when the key is in the car, but drops to 13.3V when the key isn't in the car (but car still running). I'm assuming my sub amp is going into protect mode due to overvoltage, rather than undervoltage which I originally thought. See below for details.

Ok, this one is throwing me for a loop, and I'm a tad embarrassed that I'm an electrical engineer and have to ask for help with my car sound system on the internet, especially since I've been installing car audio systems since I was 15 ?. But here I am. I posted about 6 months back in the fabulous thread started by @markboris that I installed an 8" Kicker Hideaway powered sub and powered it using the 12V conductor running to the cigarette outlet in the rear hatch (I cut the conductor and spliced it directly to my sub using a compression connector, not a tap). This is the lowest power sub I could find, and it puts out a max of 150W. Not great, but a stop gap until I want to take the time to properly run a larger conductor to the frunk to power something better. Since then, I've been going crazy because sometimes I'll feel like the sub is cutting in and out at random times, but every time I would stop my car and go back to check on it, it was working fine.

I since figured out that, yes, it was sometimes going into protect mode. My first thought was undervoltage, probably due to a poor ground connection. I had lightly sanded the paint off of my ground point, but figured I just didn't do a good enough job. So I popped the trim and cover off in the hatch again, sanded it down properly, and bolted my ground lug on with some dielectric compound. Well, this made things WORSE. Now it was definitely shutting off everytime there was any kind of bass note. So I redid my 12V positive connection with a fresh compression connector. No better. This whole time, it only seemed to stop working when I was driving my car. I was going crazy, stopping by the side of the road, walking to my trunk, just to hear my sub blasting away just fine.

So finally today, I moved my ground point to the factory amp ground point just to rule that out. Didn't fix it. This time I was out to prove I wasn't going crazy, so I climbed into the backseat without opening my driver door, and sure enough, the amp was shutting down repeatedly (light turning red indicating PROTECT mode). Finally, I pulled up car scanner to see if my LVB voltage was changing. Sure enough, when I got out of my car (with key in pocket, but car still running) to walk to the trunk, the voltage was 13.3V and my sub was happily beating along. As soon as I got in my driver seat, the sub shut down, and carscanner reported a 12V battery voltage of 14.5V. Both showing a DC-DC current of 30-35 volts. I thought maybe it was the load from the sub amp itself causing the voltage dip, so I disconnected the subwoofer amp entirely. Still does it. 14.5V when the key fob is in the car, 13.3V when the keyfob is out of the car. It's warm out, so all heaters are turned off right now, and AC isn't running. I'm assuming my subwoofer amp is disabling itself due to overvoltage rather than undervoltage, which explains why it got WORSE when I made my ground connection better, since it lowered the resistance of the ground connection.

@markboris do you have any thoughts? Ever seen anything like this? Plenty of people have installed this and similar subs without issue. My thoughts right now:

- The voltage difference based on keyfob makes no sense to me
- Even with that voltage difference, don't plenty of ICE car alternators put out ~14.5V? It seems like my amp should run fine either way, but unfortunately Kicker technical documentation isn't very good.

So yeah, I'm stumped, and sad because I'm stuck listening to podcasts because music sounds terrible with no bass (and I disconnected the factory sub).

Edit: verified both voltages with a multimeter at the sub. The OBD2 data is accurate.

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[Blue highway]

Easy test.
If it is overvoltage protection, just add a diode in series with the power to your sub amp to drop .6V as a test. If it still does it, add a second in series to drop 1.2V. If these don't get it going, it's not over voltage protection.

 

[Ride_the_lightning]

Easy test.
If it is overvoltage protection, just add a diode in series with the power to your sub amp to drop .6V as a test. If it still does it, add a second in series to drop 1.2V. If these don't get it going, it's not over voltage protection.

Good call. It's been 15 years since I worked on anything under 480 volts so sometimes the simple solutions are the easiest to miss. I do miss having a fully stocked electronics shop close by though. I'll have to make the journey over to an electronics supply shop to pick up some diodes rated for 10 amps. Only ones I can find at any stores nearby are good for 1amp. I suppose I could use Amazon or DigiKey.

Edit: Still, any thought as to why the voltage jumps when the key fob is in the car? It's instant. Car is already "running." As soon as key fob is outside the driver door, the voltage drops to 13.3V. DC-DC converter is showing as active in Carscanner both times.

 

[Mirak]

If the key is the issue, could you simply use PAAK? Or is this like a fun puzzle for you?

 

[Blue highway]

Good call. It's been 15 years since I worked on anything under 480 volts so sometimes the simple solutions are the easiest to miss. I do miss having a fully stocked electronics shop close by though. I'll have to make the journey over to an electronics supply shop to pick up some diodes rated for 10 amps. Only ones I can find at any stores nearby are good for 1amp. I suppose I could use Amazon or DigiKey.

Edit: Still, any thought as to why the voltage jumps when the key fob is in the car? It's instant. Car is already "running." As soon as key fob is outside the driver door, the voltage drops to 13.3V. DC-DC converter is showing as active in Carscanner both times.

No idea why the car behaves differently with the key in the car... but I suspect changing that behavior is not something a user can control.

 

[markboris]

Ride_the_lightning, I really don't have a clue why the voltage changes if the fob is in the car or not. I don't feel 14.5 volts should be overpowering for an amp but maybe your Kicker amp is more sensitive to overpowering than the two JL amps I am running. I like Steve's suggestion of cutting down the voltage though, so that should work for you.

 

[Ride_the_lightning]

Ride_the_lightning, I really don't have a clue why the voltage changes if the fob is in the car or not. I don't feel 14.5 volts should be overpowering for an amp but maybe your Kicker amp is more sensitive to overpowering than the two JL amps I am running. I like Steve's suggestion of cutting down the voltage though, so that should work for you.

Yeah it’s weird. They are sending me a new one under Warranty since the supported voltage is supposed to be 10-16V. We’ll see if that fixes it.

 

[markboris]

Yeah it’s weird. They are sending me a new one under Warranty since the supported voltage is supposed to be 10-16V. We’ll see if that fixes it.

I bet it will. Unless connecting to the 12v power back there is an issue or maybe it's less stable, I don't know. Haven't ever looked into any of that. Good luck and let us know how it goes.

 

[HuntingPudel]

Older GM 12SI alternators put out between 14.5-14.8V, so I would expect that those cars will have a ton of problems with your sub’s amp. Very odd. ??

 

[Mach-Lee]

Yes voltage set point changes depending on a lot of stuff such as whether the car is in gear or whether the fob is present.

Sounds like you got a bad sub that is too sensitive to voltage. Hook it up to a power supply at 15.5V and see if it stays on.

 

[Ride_the_lightning]

Solved thanks to the help of Kicker Tech support which really knew their stuff! The higher voltage present with the FOB in the car was also increasing the DC offset voltage on the high level speaker wire used to trigger the amp to turn on (went from around 6V to about 8.5V). He said that also triggers protect mode when the DC offset is higher than expected. I wired it to use the 12V pilot wire to turn on instead of DC offset and now it works great!

Unfortunately, like many things, this wasn’t documented in the Kicker manual. I would have saved my retailer the money and trouble of sending me a new unit (and me a big headache) if people would just write useful manuals that properly define the error states and conditions that lead to error states.

I still can’t get over how many times I was driving down the road and could swear the subwoofer sounded off, just to park, walk around to the back, and find it beating away like normal. 6 months of thinking I was losing my hearing (well, the hearing under 100 Hz I guess?). Like a bad April Fool’s prank.

 

[LaFong]

I wired it to use the 12V pilot wire to turn on instead of DC offset and now it works great!

What do you mean by pilot wire? This is a different wire than the main 12V supply?

 

[JohnFoxeSheets]

Unfortunately, like many things, this wasn’t documented in the Kicker manual. I would have saved my retailer the money and trouble of sending me a new unit (and me a big headache) if people would just write useful manuals that properly define the error states and conditions that lead to error states.

A friend has a Tesla PowerWall setup. He also has several UPSs for his computers and such since the switch over from grid to battery isn't sufficiently instantaneous to prevent computers from reseting. So imagine his surprise when his the batteries on his UPSs started to die even though the house was being supplied by the grid . Turns out that in certain circumstances, the PowerWalls signal the Tesla inverter by changing the frequency of the output sine wave from 60 Hz to 63 Hz; meanwhile his UPSs consider 63 Hz to be bad power, so they switch to battery! (And yeah, of course it's not documented anywhere.)

 

[SpaceEVDriver]

A friend has a Tesla PowerWall setup. He also has several UPSs for his computers and such since the switch over from grid to battery isn't sufficiently instantaneous to prevent computers from reseting. So imagine his surprise when his the batteries on his UPSs started to die even though the house was being supplied by the grid . Turns out that in certain circumstances, the PowerWalls signal the Tesla inverter by changing the frequency of the output sine wave from 60 Hz to 63 Hz; meanwhile his UPSs consider 63 Hz to be bad power, so they switch to battery! (And yeah, of course it's not documented anywhere.)

Something similar was happening to me when I was running both UPS and whole-house battery. Except instead of the UPS batteries dying, the inverter on the big battery would sometimes sense some weird backfeed and shut down the entire house. Disconnecting the UPSes "solved" the problem and our switchover was fast enough (4 ms transfer time) that my computers don't shut down even if the grid goes down.

 

[markboris]

That’s interesting John that his PowerWall’s don’t switch fast enough to not cause issues with his computers. I have mine set to power the house daily from 3pm to midnight (when there is no solar production) because that’s when my PG&E rate is at the highest. There’s never a glitch or even a flicker of lighting when this happens.

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