# Stereo head unit draining car battery



## VW-Fritzi (Mar 12, 2014)

I had a problem last spring with my car battery not holding a charge. I took it to the shop, and they replaced the battery, but also noted that it was the stereo head unit that was failing to properly switch off internally, thus slowly draining the battery. So, I ditched that stereo and bought a new Blaupunkt from Crutchfield. I installed this new one, and it worked fine for several months, but we had a cold spell last week and my battery was once again not holding a charge. I could jump it just fine and drive around for an hour, but then I'd let it sit for a couple hours and it would be dead again. I took it to the shop again, and they said it was the same problem as last time -- that the stereo was not fully turning off and thus draining the battery.

Has anyone else run into this? I know that the stereo has two power wires -- one to the ignition wire so the stereo turns on and off with the ignition, and another connected to the battery for constant power, which keeps the radio presets and bluetooth info in memory.


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## cuppie (May 4, 2005)

Need info: 
- Year/model car? 
- If car in question does not have 'switched power' for the radio (older car, like my A1 and B2 cars; or, newer car (bus-signaled)), how is the radio's switched power wired?


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## Soumatrix (Aug 12, 2014)

Did you bring in just your car battery to test? Whenever it gets colder a slow drain on your battery is pretty evident. If the battery is fine, double check to make sure the headunit is properly wired to the ignition, that's a pretty common mistake when installing headunits (though it seems like you looked into this). I'd also like to know what kind of car you drive to help more and what your previous stereo was.


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## cooper_ski (Feb 14, 2012)

Hello, I have the same problem with my OEM "Premium 7" radio on my MK5 Jetta (07). Dealer told me the radio was bad and was draining my battery. Currently the radio fuse is taken out so I don't have to jump start the car every morning. After reading the original post here, I'm now skeptic if a new radio will eventually cause the same issue.


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## VW-Fritzi (Mar 12, 2014)

Looks like the drain is coming from somewhere else. After pulling the radio, the shop recharged the battery. It was fine for a few weeks, but during another cold spell, the battery was dying again after the car sat for a few days.

I've been planning on completely restoring the entire electrical system to clean up the spaghetti mess of wiring that the previous owner(s) left me, so hopefully I'll be able to pinpoint what is causing the drain then (or just eliminate it in the process). Before then I'll be getting out the voltmeter to go fuse by fuse to see if I can locate it.


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## Trying to <3 VW (Feb 24, 2014)

Hey Fritzi,

I had this problem after installing aftermarket stereo in 2001 GTI 1.8T. Battery would drain overnight, in under 8 hrs.
It turned out that my specific problem wasn't the head unit itself, but rather its communication with the factory Monsoon Amp.

Anytime the radio turned on, it would activate the factory amplifier, but the head unit wasn't sending the right signal to turn the amp off (or the amp wasn't interpreting signal correctly??). So after driving around with the radio on and then parking and killing the engine, the amp would remain on, pulling around 1.2 Amps of current from the battery which is enough to drain it pretty quickly.

I tried phantom battery drain tests, but the problem diagnosing this for me was that as soon as you disconnect the car battery to connect your multimeter, the amp would turn off, and my meter would show no unusual current draw. After shutting off car, I had to secure my multimeter leads to the battery terminal and terminal wire BEFORE disconnecting to ensure that the circuit was never broken (and therefore turning off the amp).

Another caveat to this diagnosis is that unless I had turned the radio on after starting the car, the Monsoon Amp wouldn't ever turn on, which meant that my phantom drain test didn't show any unusual current being pulled from the battery when car was off. This made it very hard to determine what was pulling juice from the battery.

This was a headache to diagnose, so I hope this helps.


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## yeahforbes (Feb 9, 2014)

Do you have a satellite radio tuner (Sirius XM) under the front passenger's seat? Mine fried and caused a battery drain just like you're describing. It also resulted in the SAT button on the head unit causing the display to read "No Sat Radio" instead of the usual 800 number to subscribe. I guess it was the controller (CAN interface, etc.) in the sat tuner that actually went bad, causing it to be stuck on (0.5 amp draw, measured by putting my ammeter in where the radio fuse normally goes) and causing the head unit to not know it exists. It also threw some DTC's seen during a vagcom auto scan, like No Digital Radio and Digital Radio signal/communication intermittent.

I simply unplugged the tuner (super easy, right under the black plastic cover... just slide the seat back a bit) and the battery drain stopped. Never bothered to fix it, as I've never been a subscriber anyway.

2008 GTI by the way... what car is yours?


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## VW-Fritzi (Mar 12, 2014)

Sorry, I thought I had noted the year, but I've got a '75 Scirocco, with no amp.

I'm going to be doing a complete electrical wiring restoration, so hopefully I'll be able to find and/or correct the problem. The wiring under the dash is a spaghetti mess, so I'm not doing the restoration just to fix this one problem, BTW. :laugh:


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## veedubmatty (Jun 2, 2004)

yeahforbes said:


> Do you have a satellite radio tuner (Sirius XM) under the front passenger's seat? Mine fried and caused a battery drain just like you're describing. It also resulted in the SAT button on the head unit causing the display to read "No Sat Radio" instead of the usual 800 number to subscribe. I guess it was the controller (CAN interface, etc.) in the sat tuner that actually went bad, causing it to be stuck on (0.5 amp draw, measured by putting my ammeter in where the radio fuse normally goes) and causing the head unit to not know it exists. It also threw some DTC's seen during a vagcom auto scan, like No Digital Radio and Digital Radio signal/communication intermittent.
> 
> I simply unplugged the tuner (super easy, right under the black plastic cover... just slide the seat back a bit) and the battery drain stopped. Never bothered to fix it, as I've never been a subscriber anyway.
> 
> 2008 GTI by the way... what car is yours?


Good lord. My MK5 GTI battery has been draining forever. I just unplug the battery every night. no sat available on my radio also. I've known it was my radio circuit but had no idea the sat was the problem. I just went out and checked voltage across the radio fuse while I unplugged the sat radio. drain disappeared. Thank you!


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## dash200 (Sep 22, 2021)

yeahforbes said:


> Do you have a satellite radio tuner (Sirius XM) under the front passenger's seat? Mine fried and caused a battery drain just like you're describing. It also resulted in the SAT button on the head unit causing the display to read "No Sat Radio" instead of the usual 800 number to subscribe. I guess it was the controller (CAN interface, etc.) in the sat tuner that actually went bad, causing it to be stuck on (0.5 amp draw, measured by putting my ammeter in where the radio fuse normally goes) and causing the head unit to not know it exists. It also threw some DTC's seen during a vagcom auto scan, like No Digital Radio and Digital Radio signal/communication intermittent.
> 
> I simply unplugged the tuner (super easy, right under the black plastic cover... just slide the seat back a bit) and the battery drain stopped. Never bothered to fix it, as I've never been a subscriber anyway.
> 
> 2008 GTI by the way... what car is yours?





yeahforbes said:


> Do you have a satellite radio tuner (Sirius XM) under the front passenger's seat? Mine fried and caused a battery drain just like you're describing. It also resulted in the SAT button on the head unit causing the display to read "No Sat Radio" instead of the usual 800 number to subscribe. I guess it was the controller (CAN interface, etc.) in the sat tuner that actually went bad, causing it to be stuck on (0.5 amp draw, measured by putting my ammeter in where the radio fuse normally goes) and causing the head unit to not know it exists. It also threw some DTC's seen during a vagcom auto scan, like No Digital Radio and Digital Radio signal/communication intermittent.
> 
> I simply unplugged the tuner (super easy, right under the black plastic cover... just slide the seat back a bit) and the battery drain stopped. Never bothered to fix it, as I've never been a subscriber anyway.
> 
> 2008 GTI by the way... what car is yours?


Omg thank you god was so confused why my car keep draining so quick u are a life saver


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