Battery drain

[Shapple]

Got a subwoofer in the car. Previously worked fine. Still plays audio and everything, but when it is hooked up to the battery, it drains it completely within 48 hours. And I mean completely, my fob won't even work. I imagine I have a short or something? When I disconnect the amp from the battery, the battery is fine and does not drain, so I've isolated the problem to the audio system. Or an improper ground? It was installed professionally which means all my wires are below the floorboards which makes it difficult to just check that all the wiring is correct. I have a volt meter. I dont know what setting I would use on it, or where I need to check the voltage. Thanks for your help.

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[Popwarhomie 5,000+ posts]

Is the amp turning off when the key is turned off?

What amp?

 

[Lasherž]

Got a subwoofer in the car. Previously worked fine. Still plays audio and everything, but when it is hooked up to the battery, it drains it completely within 48 hours. And I mean completely, my fob won't even work. I imagine I have a short or something? When I disconnect the amp from the battery, the battery is fine and does not drain, so I've isolated the problem to the audio system. Or an improper ground? It was installed professionally which means all my wires are below the floorboards which makes it difficult to just check that all the wiring is correct. I have a volt meter. I dont know what setting I would use on it, or where I need to check the voltage. Thanks for your help.

Amps usually have lights, so you should be able to tell if it's on just by looking at it while the car's off. If your amp doesn't have a light then measure voltage between the signal wire and ground. If it's receiving voltage on signal while the car's off then it wasn't set up correctly. This could be an error on the other side of the signal cable, wherever it goes to either the fuse box or the the back of the radio, or more likely there's a tiny strand of wire sticking out of the terminal and poking into the positive lead area. Signal cables barely use any current, so a single strand of the wire will be enough to keep the amp powered on all the time.

If it's not a stray wire at the terminal then take it back to the professional and get them to set it up correctly free of charge because that's likely to do damage to your battery if it hasn't already and that implies they didn't use a proper fuse for signal source or otherwise know what they're doing on the first go.

 

[Shapple]

Amps usually have lights, so you should be able to tell if it's on just by looking at it while the car's off. If your amp doesn't have a light then measure voltage between the signal wire and ground. If it's receiving voltage on signal while the car's off then it wasn't set up correctly. This could be an error on the other side of the signal cable, wherever it goes to either the fuse box or the the back of the radio, or more likely there's a tiny strand of wire sticking out of the terminal and poking into the positive lead area. Signal cables barely use any current, so a single strand of the wire will be enough to keep the amp powered on all the time.

If it's not a stray wire at the terminal then take it back to the professional and get them to set it up correctly free of charge because that's likely to do damage to your battery if it hasn't already and that implies they didn't use a proper fuse for signal source or otherwise know what they're doing on the first go.

I do not think the amp light is always on, but i will double check.

When it was installed, it worked fine for multiple years. At some point it started draining my battery.. I can't remember if that was before or after I bought the new CD player for the car. I think it was before, and when I bought the new CD player I hoped it would fix it but it didn't. . Is there a ground wire on the CD player that I may have missed? Could that cause such a battery drain?

As far as measuring voltage between signal wire and ground. I think the signal wire is the skinny blue cable. It's not thick like the rest. I would take my volt meter and hold the positive to the blue cable and the negative to the ground cable? What voltage setting should the volt meter be at? The signal cable goes to the back of the radio.

When I look at the cables going to the Amp, they all look pretty clean. Well attached. I did install the CD player myself ,maybe I messed that up? But like I said, I think i had this problem before I bought the new Cd player.

If my ground from the Amp became disattached from the chassis, would that cause such a drain?


Thanks for your help.

 

[Lasherž]

I do not think the amp light is always on, but i will double check.

When it was installed, it worked fine for multiple years. At some point it started draining my battery.. I can't remember if that was before or after I bought the new CD player for the car. I think it was before, and when I bought the new CD player I hoped it would fix it but it didn't. . Is there a ground wire on the CD player that I may have missed? Could that cause such a battery drain?

As far as measuring voltage between signal wire and ground. I think the signal wire is the skinny blue cable. It's not thick like the rest. I would take my volt meter and hold the positive to the blue cable and the negative to the ground cable? What voltage setting should the volt meter be at? The signal cable goes to the back of the radio.

It doesn't really matter what voltage range your meter is set for, just DCV. Something that includes 15V DC.

The CD player could also be the problem. Head Units use about 1 amp standby and amps use about 2 to 4 depending on their class. You could start by telling us what the drain is from the battery when it's off. Wait like 5 minutes after turning off the car with the hood up and all the doors shut, then remove the positive battery terminal and use current mode on your multimeter to bridge the gap between the removed wire and the positive battery post it came off. It's important for everything to be off to get a good reading and to protect your multimeter from damage from too high of current.

When I look at the cables going to the Amp, they all look pretty clean. Well attached. I did install the CD player myself ,maybe I messed that up? But like I said, I think i had this problem before I bought the new Cd player.

If my ground from the Amp became disattached from the chassis, would that cause such a drain?


Thanks for your help.

Looking clean isn't really enough to be sure in a car, 12V isn't very much and grounding issues are the most common electrical issue because of it. That being said, the connections themselves would only be a problem if something was shorting from either the signal to the positive or the positive to the negative. The more likely of the two is that there's a frayed wire between the small blue cable and the big red cable keeping your amp on. Let me know when you figure out if the amp is staying on, that's still step one.

Push comes to shove you can always disconnect your radio again and rerun the current drain test, if the drain goes away it's either a defective radio sending signal to the amp constantly (unlikely) or there's something wrong with the hookup on the radio. Most likely the ignition wire isn't turning off with the ignition and it's staying on all the time instead. That will result in about a 600-1000mA draw constantly.

Grounding doesn't cause drain issues like this.