[Power]How to solve the car battery drain issue on new aftermarket radio stereo?

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[Power]How to solve the car battery drain issue on new aftermarket radio stereo?

Postby Andy » Tue Jan 26, 2016 7:20 am

Some of clients may happen to face the car battery drain issue after installed a new after market Radio DVD GPS stereo, and they are not able to find the reason.
Before we start checking, we need to understand how does the after market Radio DVD GPS stereo get power to work. No matter what kinds of after market Radio DVD GPS stereo you get, it will include power cable adapter which used to connect between the new unit and the original car connector.
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Expect for those unit which is already built in the plug to the body rear for direct plug with original car connector.
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Then you check at the power harness on the radio side, you will find 3 wires with color yellow, red and black, normally use bold wire compare to other wire from the harness. Those 3 wires are for power supply to the radio.
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Now let’s see where the three wires should be connected to and how does they function.
Bold Black wire
It is GND(ground) wire, it should be connected to 12V negative pole of the car battery power supply wire. Some installer also connected it to the car metal body to direct ground it, which is also ok, just make sure it was grounded good as it is the ground wire of the whole unit.
Bold Yellow wire
It is BAT+ wire, it should be connected to 12V positive pole of the car battery power supply wire. It should be permanently connected with power, because it is also power to the radio’s memory IC. Once the power disconnected, all the settings will be lost and not save.
Red wire
It is the ACC wire, it should be connected to a switched 12V live positive wire from the car. It controls the radio for turning on and off. Once it get power, it will release the power from the yellow wire and lead the power enter into the radio to turn on all functions to work. Once it disconnect from power, it will cut the power from the yellow wire, only keep the yellow wire’s power for small memory IC for keeping setting data.

If the yellow wire and black wire are connected correct, but the red wire being connected with permeation power, then the radio will drain car battery. Most of the battery drain issue are caused like this, and customer are just simple press the power button on the radio, and think the radio is already turned off manually, but actually the radio is just in standby condition and waste power still.

So the first thing we need to check is that whether the red wire connected correct, it should be disconnect from power when you pull out the car key, and the radio should be automatically turned off. If not, then the wire is connected wrong, you need to find a switched wire from the car to connect, such as the cigar lighter positive pole.
There is another situation may think about, that if you have joint any wire to the yellow wire. Cause the wire is constantly with 12V power from car battery even if car key removed, if you connected any wire to this wire to get power, then it will also drain car battery.

If above are checked but still drain battery, then it maybe the radio is problem or any other area problem from the car, you may need to contact a car shop to check.

If the unit is can bus decoder controlled device, such as Volkswagen device, you may found out that the red ACC wire is comes out from the can bus box and goes to the radio, instead of direct connect with the original car connector wire. And you may also found out that the can bus box is also gain power from the yellow wire. If the red wire is disconnected from power when car key removed, then the most possible situation will be the can bus box drain power, and it either the can bus faulty or the can bus do not compatible with your car’s system. You may do a small wire modification to power the can bus decode box from the cigar lighter positive pole to check whether it is still drain car battery, so the can bus will disconnect power from battery when removed car key.
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