Deck turns on when battery is low and car is off

[Dragonsyph]

Been having a bad drain problem the last year, can’t figure what it is.

But the main problem is, when the drain gets the battery’s low enough the head unit will start playing sound, but the head unit screen is off and blank.

What could be causing this? As this them drains my battery’s dead in a single night.

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[Dragonsyph]

Also this all happens when the car is off. And when on it all works fine.

 

[mahc 10+ year member]

What if you take out the radio fuse?

 

[Mitchell Fosgate III]

Been having a bad drain problem the last year, can’t figure what it is.

But the main problem is, when the drain gets the battery’s low enough the head unit will start playing sound, but the head unit screen is off and blank.

What could be causing this? As this them drains my battery’s dead in a single night.

The head units are OP AMPs. It only takes about 0.0000450 Microvolts to turn on the transistors to the radio. Not a lot of power needed to catch a reception. Parts of the radio works, the screen doesn't work. It's broken cannot get it back. Get a new one or get that one repaired. Internally it's running on capacitors, the IC then is already dead or shut off or closed. Soon nothing will be on. Buy another one or get this one checked. Burnt out diodes, resistors, or transistors.​

 

[Jimi77 Premium Member]

OP, are you saying the HU comes on when the battery voltage is low and thus the battery drained even faster???

 

[highfigh]

Have the battery tested- when it totally discharges, you lose about 30% of its capacity, every time.

Buy a multimeter and test light with incandescent bulb, then learn to use them. Do a Current test on each piece of equipment, to see what's causing the drain. Pull the radio fuse and the main fuse or breaker for the whole system and let it sit overnight- if it doesn't, continue with the diagnostics of the stereo, but if it does, disconnect the battery and measure current with the key out of the ignition switch, doors closed and all lights off. If you see more than about 15mA, especially if it's around 300mA, you need to have the alternator repaired. If you see whole numbers, start pulling fuses, one at a time and replace them if nothing changes. Once you pull the fuse that causes the draw to stop, fix whatever it is.

I don't know what's in your system but if you added amplifiers that draw a lot of current and DIDN'T add a heavy ground cable connecting the body and battery under the hood, do that.