Alternator doesn't charge at idle (SOLVED)

5th February 2014, 16:22

Hello there,there's a electrical draining on my VTS when it is off,discovered this as i was able to turn my diagnostic tool on despite the car being off and no key in the ignition.

I did some check and all of the fuses in engine bay are okay,only checked a couple inside but they were good too,the radio works fine and is not draining anything when off,battery light is on but the battery itself is new,before purchasing the car it was not driven for days and when i tried to turn it on it really struggled,probably because of said draining and the battery was almost flat,i got it to start and not turn off only after several times.

I will soon buy a multi-meter and see if the alternator is effectively charging the battery when the car is on.

Any idea what's draining the battery? Many thanks.

5th February 2014, 16:27

I have a similar problem, checked the battery and alternator, both fine. I tried disconnecting my sub and it still seemed to drain. Help for me too please

5th February 2014, 16:34

Run the multimeter across each the top of each fuse when the ignition is off to find out which circuit or circuits are causing the drain.

5th February 2014, 16:47

I had the same with my sax, I found it to be a setting on head unit not turned on "power save mode" some cars it drains the battery as stated in my manual for the head unit (pioneer unit) so might be worth a check to see if its the issue?

Hope you get it sorted, nothing worse than getting to the car and not being able to start it ><

5th February 2014, 16:51

Quote:

Originally Posted by Saxman2014

I had the same with my sax, I found it to be a setting on head unit not turned on "power save mode" some cars it drains the battery as stated in my manual for the head unit (pioneer unit) so might be worth a check to see if its the issue?

Hope you get it sorted, nothing worse than getting to the car and not being able to start it ><

Disconnected the radio completely and it was still draining somewhere,thanks for the tip anyway.

5th February 2014, 16:53

Quote:

Originally Posted by VeiRoN

Disconnected the radio completely and it was still draining somewhere,thanks for the tip anyway.

Time to get the ol' volt meter out then I'd say!

5th February 2014, 18:30

Quote:

Originally Posted by Kebabman

Run the multimeter across each the top of each fuse when the ignition is off to find out which circuit or circuits are causing the drain.

Should i put the multi-meter to resistence Ω?

5th February 2014, 18:32

If you go on YouTube and type in current drain there's a guy showing how to test with a multimeter.i would bet though that the alternator is causing it,is your boot shut completely(thinking courtesy light)?

5th February 2014, 18:33

Quote:

Originally Posted by VeiRoN

Should i put the multi-meter to resistence Ω?

No, you want to measure the current draw so measure the amps.

5th February 2014, 19:25

Quote:

Originally Posted by stevo67

If you go on YouTube and type in current drain there's a guy showing how to test with a multimeter.i would bet though that the alternator is causing it,is your boot shut completely(thinking courtesy light)?

Yes it is,courtesy light stays off.

6th February 2014, 17:04

Okay so,turns out that the diagnostic toll matter is normal and so it does not mean nothing and i can't say something is draining the battery because of that,my bad,sorry about that.

Anyway i got the alternator tested and it seems like that the alternator doesn't charge when the car is at idle,it works just fine when accelerating a bit,we tried at around 2k rpm,as it charges at 14.2v,now i've to find out why it won't charge at idle.

6th February 2014, 18:47

Don't forget the alternator is spinning faster at 2k so if say the alternator voltage regulator is goosed then the extra revs would compensate for its fault.which is why at idle it doesn't kick out the correct voltage.

6th February 2014, 19:45

Okay i guess i just need to replace it if that's the problem,the alternator is also noisy when cold and the car is at idle,said noise disappear after 2k rpm,also it gets a little louder if you keep your finger on the window switches when they are fully closed.

6th February 2014, 19:59

The noise is probably worn alternator bearings mate.

6th February 2014, 20:24

One other thing that can cause a noise and poor charging on a vts,is the crank pulley there is a rubber insert on the pulley which wears away.this causes slipping and poor charging.it would not though account for battery drain.

6th February 2014, 20:35

Quote:

Originally Posted by stevo67

One other thing that can cause a noise and poor charging on a vts,is the crank pulley there is a rubber insert on the pulley which wears away.this causes slipping and poor charging.it would not though account for battery drain.

Well there's also a squeaky noise that becomes louder as the revs increase,it seems like an electric motor and you can clearly hear it when going at low speed,thanks for the help.

6th February 2014, 23:12

If your battery light is on all the time, one of the diodes in the diode pack has failed by the sounds of things.

Simply unplug the alternator and do a current test again.

Which means only 2 (or even 1) of the phases are working which means reduced charge and no charge at idle.

I would guess that the uneven load can cause a whine too.

7th February 2014, 14:30

Another thing to try to eliminate the alternator would be to fully charge the battery connect it back up,but disconnect the alternator & leave overnight.Check the battery charge in the morning if its still fully charged then the alternator is at fault.

7th February 2014, 17:25

Quote:

Originally Posted by VeiRoN

Okay so,turns out that the diagnostic toll matter is normal and so it does not mean nothing and i can't say something is draining the battery because of that,my bad,sorry about that.

Quote:

Originally Posted by stevo67

Another thing to try to eliminate the alternator would be to fully charge the battery connect it back up,but disconnect the alternator & leave overnight.Check the battery charge in the morning if its still fully charged then the alternator is at fault.

Hi,if you're talking about the draining issue i updated my post earlier and removed this possibilty as the diagnostic tool thing doesn't mean anything.

7th February 2014, 19:01

Quote:

Originally Posted by VeiRoN

Hi,if you're talking about the draining issue i updated my post earlier and removed this possibilty as the diagnostic tool thing doesn't mean anything.

Well, in that case!

If your battery light is on all the time, one of the diodes in the diode pack has failed by the sounds of things.

Which means only 2 (or even 1) of the phases are working which means reduced charge and/or no charge at idle.

Or the regulator is dying.

Battery lights often flicker slightly when driving fast if you have an old/worn belt or it's needing tensioned.

You should be getting 13.1v at idle (750rpm) minimum

10th February 2014, 17:52

Update: I gave a good clean on the metal connector on top of the alternator and replaced its rusty nut,now the battery light flashes pretty much all the time,it goes away when the car is moving and when it is idle sometime it comes back and keep flashing or sometime it just goes away.

10th February 2014, 18:09

From what you've just said it sounds like a faulty diode in the alternator mate.

10th February 2014, 19:34

2nd update: Drove it a little bit more and noticed that when the car is cold the light comes on,it's steady for a few minutes then it starts to flashes then it goes away in 2-3 minutes until you turn the car off and it is cold again.

SOLVED: The 2 pin connector on top of the alternator was loose causing it to not charge properly.