battery light on when headlights turned on

[justice4all3000]

my battery light comes on when headlights are turned on what should i do??

[accentstencil]

Get your battery and alternator checked by an auto electrician.

[m1lky]

With the car idling check the voltage across your bat. Should be at least 13v

[justice4all3000]

with the engine running and accesories running (headlights, AC, stereo ect) the batt is at about 14 volts however when i turn the rear demister on also it drops to about 12.3 volts is that ok?

[TonyJZX]

i would say no

should be 13.8 no matter what is going on

short? leak? in the rear demister circuit?

[justice4all3000]

i would say no

should be 13.8 no matter what is going on

short? leak? in the rear demister circuit?

How do I test the rear demister for problems?

Thanks

[m1lky]

Unplug it off the window. Probably under the pillar cover. Pull the fuse. Test for continuity on the car side of the connector not the window side (you shouldn't have it)

[justice4all3000]

Unplug it off the window. Probably under the pillar cover. Pull the fuse. Test for continuity on the car side of the connector not the window side (you shouldn't have it)

thanx will give it a try

[BlackVXGTS]

Replace your voltage regulator. Easy and cheap fix. The bushes in the regulator wear down over time and result in the alternator not being able to keep up its normal charge rate. Vary your test by leaving the headlights off and the rear demister on and see if the battery light comes on. If it doesn't then turn the headlights (I assume you had high beam on) to see if the battery light comes on. That should establish if the problem is the rear demister or the regulator (or some other part of the alternator).

[justice4all3000]

yesterday the battery light came on again, this time the rear demister was not on so i doubt its the cause of the problem. Where can i get a voltage regulator from? do i have to remove the alternator to replace it? (series 1 v8)

[m1lky]

With the car idling check the voltage across your bat. Should be at least 13v

Test your alternator and reg first. With high beam on for a decent load.

You can do it yourself as above or chat to autosparkie. He'll prob do it for free.

Alternators wear out at the end of the day. Shouldn't be too hard to replace if it has. I'd get yours reconned or a new one rather than second hand

[justice4all3000]

just tested it with a multimeter with the engine running again its putting out 14.5 volts and when i turn on all of the accessories on it drops to 12.4 volts however if i keep the enging revving a tiny bit the voltage will return to 14.5 volts does this definitely mean that the alternator is to blame I just dont want to waste my time and money replacing it if its somthing else!

thank you to everyone who has been helping me with this

[m1lky]

Seems like it's not keeping up to me.

Are your battery terminals tight and clean?

I'd replace alternator (would assume regulator is inbuilt). If your worried take your car to an auto sparkie first they can test it

[justice4all3000]

I recently put in a one year old battery out of a vn v6 could that have anything to do with the problem?

[wrx884]

its ur regulator on its way out, not the alternator.

with the car off wat does ur battery read? if its around 12.5V then its fine and not that either.

[justice4all3000]

thinking about replacing the alternator with a secondhand one (tested with warrenty) is that a good idea or should i go brand new?

[wrx884]

regulator $15, u can go through 2-3 of them b4 needing a new alternator ud b best 2 do that 1st.

[justice4all3000]

regulator $15, u can go through 2-3 of them b4 needing a new alternator ud b best 2 do that 1st.

where can i get one from? bursons?

[wrx884]

Any auto store that sells parts should have them as they r fairly common. (not sure wat bursons is dont think we have 1 of those in perth lol).

[justice4all3000]

can the voltage regulator be replaced without removing the alternator?

[justice4all3000]

ok replaced the voltage regulator with a brand new one the voltage its at a steady 14.3 volts however if i turn absalutly accessory on the voltage hangs around 12.5 to 13 the battery light hasnt come on yet

[wrx884]

check all ur grounds now and if u got a sound system in the car have u done the Big 3 upgrade? even if u havent its not a bad idea 2 do it and it helps alot specially if u use alot of accessories. its just upgrading all ur grounding wires in the bay.

if it still fails get the new regulator checked out and make sure its working fine ive had brand new genuine regulators fail on me b4.

[justice4all3000]

how do i upgrade the grounding wires?

[wrx884]

big 3 upgrade - VY Commodore

It 4 VY but its pretty much the same principle.

[justice4all3000]

took the car to an auto elec today got everything tested it seems that replacing the voltage regulator fixed the problem and i was told that its normal for the voltage to drop to around 12 while idling with the accessories on. I will probly do the "big three upgrade" when i get round to putting a sub and amp in