Amplifier and sub causing battery to drain while driving???

[Dave S]

I’ve been having the dreaded check 4x4, service vehicle soon, warning lights come on for almost 9 months now on my 2022 Base Mansquatch 2 door. The codes thrown are saying the battery has low state of charge, similar to TSB 23-2182. Been to my dealer over six times to try and fix the issue. First they blamed my added lights and accessories causing the the battery to drain. Later, they replaced my 4x4 control module and the problem went away for several months.
Problem came back and they told me I wasn’t driving enough, as the Bronco is not a daily driver, and recommended I use a battery tender charger/maintainer. I did that and still got several check 4x4, service vehicle soon lights.
Back at the dealer now and they are now telling me that my amplifier and sub are causing the battery to drain while driving. I have a Rockford Fosgate 750 watt 5 channel amp and the stinger tailgate 12” sub, along with all new/upgraded speakers which were installed by a very reputable audio/stereo shop that’s been around for 30 years.
I was curious if anyone else has heard of this happening with an upgraded sound system. My Ford dealer is saying I will probably need to add an additional battery to power the amplifier. Weird thing is I had been running the upgraded sound system for six months before my first check 4x4 service light.
I plan on driving the Bronco for a week or two to see if the check 4x4 light comes back on while the amp is disconnected before bringing it into the audio/stereo shop where I got the work done to see if they can fix the issue.
Any help or suggestions would be appreciated.

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[Karl_in_Chicago]

For the system you describe there's no way it's "draining the battery" while your vehicle's running. There are soooo many people running considerably more demanding sound systems with stock electricals. Now that's not to say that some of the electrical work that's been done, or even factory wiring, doesn't have some type of short/ground somewhere that's running down the battery - but, all other things working correctly, the dealer suggesting that (relatively) modest amp's demands are to blame is laughable.

 

[FreddieLee]

Draining while running? How many volts do you see while driving?

How did the service department reach that conclusion? Did they attach a DMM, and start pulling fuses, or see if the amp is drawing current with the ignition off, or per norm, are they just guessing?

How does the amplifier power on, via a remote turn-on wire, a signal-sensing feature, etc?

What's the amplifier ground to?

 

[JeffL]

how long does it sit? do you leave it locked? I've found when my bronco sits in the drive way unlocked the computer keeps turning on to keep it in "ready" mode? But every time it turns on both my amps come on and the subs will even pop a little. i had my installer remove the auto on signal to the amps and put in a simple on / off switch. I never had a battery problem, some times my bronco will sit not driven for a week or so, but maybe something to consider?

 

[Dave S]

Draining while running? How many volts do you see while driving?

How did the service department reach that conclusion? Did they attach a DMM, and start pulling fuses, or see if the amp is drawing current with the ignition off, or per norm, are they just guessing?

How does the amplifier power on, via a remote turn-on wire, a signal-sensing feature, etc?

What's the amplifier ground to?

According to the dealership the battery state of charge was going down when the amp was plugged in and the vehicle was running and the check 4x4 light would come on randomly. When they unplugged the amp they said the battery state of charge would increase as normal and they couldn’t get the check 4x4 light to come back. They did not provide with with specifics of voltage with the amp plugged in versus not plugged in. It’s just weird that I went six months without issue with the amp but who knows, maybe it went bad or a wire came loose. I’m going to wait a week or so and then bring it to my audio/stereo guy.
I’m not sure where the ground wire for the amp is unfortunately, I’m not too familiar with audio/stereo work. The amp is under my drivers seat but all the wires are hidden so I’m not sure where the main amp ground wire is connected to. When I turn the ignition off the amp turns off so I’m not sure what kind of remote or sensor they used for it to do that. Other than the main power wire for the amp with the fuse going to the battery, there is also a smaller red wire and ground wire connected to the battery as well. Wish I could tell you what they were for haha.

 

[Dave S]

how long does it sit? do you leave it locked? I've found when my bronco sits in the drive way unlocked the computer keeps turning on to keep it in "ready" mode? But every time it turns on both my amps come on and the subs will even pop a little. i had my installer remove the auto on signal to the amps and put in a simple on / off switch. I never had a battery problem, some times my bronco will sit not driven for a week or so, but maybe something to consider?

I drive it pretty regularly, at least every weekend and sometimes during the week for small errands. I usually keep it in the garage and unlocked. My amp only turns on when the ignition is on and I’ve never heard it make noise with the ignition off. It’s just weird the battery problem occurs when I have been driving for 15-20 minutes, I would think the alternator would keep the battery charged. I’m waiting a week and then will bring it to my audio guys to make sure there isn’t a loose wire or the amp went bad or something. I’ve never had an issue with the music cutting out or anything, so it’s kind of weird.

 

[HeliPilot]

There is a specific way to hook up the battery tender. If not hooked up properly, the bronco doesn’t recognize it and will show battery depletion. There is a micro processor at the battery, and you must be on the correct side of it while charging. Of course, you could just have a sh** battery.

 

[Dave S]

According to the dealership the battery state of charge was going down when the amp was plugged in and the vehicle was running and the check 4x4 light would come on randomly. When they unplugged the amp they said the battery state of charge would increase as normal and they couldn’t get the check 4x4 light to come back. They did not provide with with specifics of voltage with the amp plugged in versus not plugged in. It’s just weird that I went six months without issue with the amp but who knows, maybe it went bad or a wire came loose. I’m going to wait a week or so and then bring it to my audio/stereo guy.
I’m not sure where the ground wire for the amp is unfortunately, I’m not too familiar with audio/stereo work. The amp is under my drivers seat but all the wires are hidden so I’m not sure where the main amp ground wire is connected to. When I turn the ignition off the amp turns off so I’m not sure what kind of remote or sensor they used for it to do that. Other than the main power wire for the amp with the fuse going to the battery, there is also a smaller red wire and ground wire connected to the battery as well. Wish I could tell you what they were for haha.

Actually I was mistaken, the smaller red wire and ground are to my ditch lights. Not sure why the dealership unplugged it. My mistake.

There is a specific way to hook up the battery tender. If not hooked up properly, the bronco doesn’t recognize it and will show battery depletion. There is a micro processor at the battery, and you must be on the correct side of it while charging. Of course, you could just have a sh** battery.

yep, when I used the battery tender I made sure the ground was connected to the far end of the minder so it recognized the charge. The dealership replaced the battery but were still getting the check 4x4 light while driving.

 

[Brian_B]

While the engine is running, it’s the job of the alternator to keep the battery topped off. Short of some very large loads (like running a winch non stop or some very, very large subwoofer amps) - a working battery and alternator will run everything on the vehicle at the same time more or less forever.

So - no, your amp is not draining the battery while the car is running.

My guess is battery is shot, although you stated it was replaced. Did they do the battery reset?

 

[Dave S]

While the engine is running, it’s the job of the alternator to keep the battery topped off. Short of some very large loads (like running a winch non stop or some very, very large subwoofer amps) - a working battery and alternator will run everything on the vehicle at the same time more or less forever.

So - no, your amp is not draining the battery while the car is running.

My guess is battery is shot, although you stated it was replaced. Did they do the battery reset?

They replaced the battery and told me the check 4x4 light came on after due to a low battery state of charge. Then they unhooked the amp and told me the battery state of charge was normal. They didn’t provide any specifics though, like what the actual voltage readings were when the amp was hooked up and when it wasn’t. I’ve been driving it all weekend and no check 4x4 light so far with the amp disconnected, so maybe something did happen with the amp or wiring. Gonna bring it to my audio guy in a week or so to have him check. Just weird because the music has never stopped or skipped or anything like that while driving.

 

[Brian_B]

The amp has a fuse right? Usually out near the battery (that’s probably how they unhooked it)

 

[Dave S]

The amp has a fuse right? Usually out near the battery (that’s probably how they unhooked it)

They disconnected the main power wire from the battery. The fuse is a few inches down the wire from the connector.

 

[Brian_B]

They disconnected the main power wire from the battery. The fuse is a few inches down the wire from the connector.

How many amps is the fuse? I’m guessing 100A

 

[FreddieLee]

If they installed the amplifier under the drivers seat, it was probably ground to the lower seatbelt assembly bolt, which isn't an appropriate ground point. The folks that have successfully used that location to ground probably cranked that bolt down super tight.

Assuming that's the problem, among other issues, a bad ground causes resistance in the electrical system, so while the amplifier is drawing power from the electrical system, the resistance it encounters during draw causes the voltage to drop. The drop in voltage can create a condition in which the battery cannot recharge. The more common alternative to that is the amplifier goes into protection mode, and simply shuts itself down.

Again, that's assuming that you have a bad ground connection.

Without a multimeter, the easiest way for you could check that would be to add the battery voltage meter to your display, go for a drive and monitor the voltage. Reconnect your amplifier, go for a drive, crank the music up, and see if the voltage drops.

 

[Riverwood]

Curious of the solution here? I’m now dealing with this on my bronco out of nowhere and also have a sub on the back door that came with the car when I bought it

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