Whats the voltage of the battery when the car is idling?

 

Sorry, poor wording. I was referring to after start-up, when the battery needs to get charged up from the alternator and doesn't get the flow required for charge.

 

Should be around 14V assuming the battery is fully charged and no large electrical loads. It should not drop below 13.5V even with a large load ant at 1500 rpm. Once it reaches this point it's time for a new alternator.

 

There's your problem. The old ground wire that was in your engine bay gets tossed in the trash. The battery should now be grounded to the body/chassis in the hatch area. You obviously need to run the power wire up to the engine bay, but the ground wire doesn't run back up there. The ground wire needs to be as short as possible. I try to keep it less than 24".

 

You still need a ground wire to the engine block capable of carrying the starter current. I will take all my grounds and link them together with the appropriate sized wire. Usually just 14 ga for the small stuff and #6 for the main grounds.

 

That's what the ground cable going from the engine to the chassis does. That has nothing to do with the battery ground. Ground a remote battery within 24" of the battery, don't run the cable back up to the engine bay.

 

just add another ground to the chassis close to the battery and keep the one that runs the length of the car. just keep adding ground points until the whine disappears. i have done it on multiple applications usually for stereos. grounding the alt casing seemed to always make the biggest difference in most cases.





find some wire and start grounding different points while you can hear the whine and u will be sure to fix it.

 

It's common for Asian cars to use the chassis as the ultimate ground. But it also brings problems with age as the chassis starts to rust or corrode.



Most alternator whine is either bad ground at the sound equipment or power and audio wires running near each other.

 

All the electrical power comes from the alternator. It has to all return to the alternator case via the ground. It is a good idea to add a major ground in copper from the alternator case to the engine block. Then a good copper ground from the block to the battery.