Hi,
As per heading: My charge light is coming on after about 20 min of driving.
It does not come on under acceleration, only when I back off.
I have changed the battery, as It was time for a change,
I have changed Positive and Negative Battery terminals as I found the Negative one had cracked.
Battery mounted in boot in secure box
This problem has never occurred before.
Could it be an Earth, resistor or alternator issue??
I have searched the forum, finding that it may be an earth issue?

Any thoughts before I go tearing bits apart and have to get a professional in would be greatly appreciated!
With thanks

_________________
2010 Landcruiser (work)
06 CAT24M Grader - daily
2011 White Subaru Impreza - daily
70 1600 White Old School with L18
77 200B SX Stock Blue retired to pickapart VIC

do you have a multimeter? test the voltage going in and coming out off the alternator

If the belts not loose or stretched only drive for 15 minutes

As mentioned ^ check what terminal voltage you have when the Charge lamp comes on.
Barring loose belts or electrical connections, I would suggest that the alternator brushes may be worn down resulting in lack of spring pressure on them.
That causes them to "float" and thus reduce the efficiency of the exciter winding, resulting in reduced output.
They should be easy to check and cheap to replace.
If not worn, then the next suspect would be the Voltage Regulator.
Do some voltage checks first though.
Battery voltage at rest - 12V.
..........."...."....... idle - 13.8-14.2V CONSISTENT!
..........."...."....... driving speed - 13.8 - 14.2V CONSISTENT!

_________________
Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

The same thing happened on my old magna. also when driving at night the head lights would not be as bright fading on and off and it was the alternator.

Cheers,

Richard.

Thank you all for your constructive and prompt replies.
Multimeter will be sourced,
Voltage checks to be done.
Cheers

_________________
2010 Landcruiser (work)
06 CAT24M Grader - daily
2011 White Subaru Impreza - daily
70 1600 White Old School with L18
77 200B SX Stock Blue retired to pickapart VIC

When Possible get a in car volt meter(NOT AMP METER) so you can always monitor the voltage while driving and under load with accessories on. it will give you a indication of whats breacking down way before the IGN light come on.

There are even some cheap plug in Cig light type ones now that work pretty good that I have used before

most like as Nissanman said its the brushes as Mine would do the same. Work at High RPM

My thoughts too.
To prove it, when your lights go dim while the car is running, tap the rear of alt body firmly with a rubber mallet etc and you should see the lights go bright again and the voltage jump up to ~13.5
Common fault...

Quick update:
Taking all the advice of you fine people on board I got my alternator serviced.
New brushes, bearings and regulator.
Fan belt tension to correct play

Re installed just now - CHG light coming on at idle
Battery voltage at idle 12.3 Volts consistent.

CHG light goes off at engine speed
Battery voltage at 2000rpm 12.3 Volts consistent.
This is obviously too low as it should be around 13 - 14V as Graeme posted before.

Any suggestions would be greatly appreciated.

_________________
2010 Landcruiser (work)
06 CAT24M Grader - daily
2011 White Subaru Impreza - daily
70 1600 White Old School with L18
77 200B SX Stock Blue retired to pickapart VIC

Hmmmmm!
Is the alternator internally regulated or externally?
If It is EXTERNAL then that box may be schtuffed!
I have very recently been down this path.
My Voltage Regulator was epoxy sealed at the rear, cork gasket on the lid, totally corroded electronics on the inside!
Moral: As Archimedes once said, "You can seal moisture IN but you can't seal it OUT!"

_________________
Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

I sent you pics of my alternator Graeme, can you tell from that?

_________________
2010 Landcruiser (work)
06 CAT24M Grader - daily
2011 White Subaru Impreza - daily
70 1600 White Old School with L18
77 200B SX Stock Blue retired to pickapart VIC

If you have a metal box mounted to the front of the rh side strut tower in the engine bay its most likely externally regulated.
That box is the regulator...

It looks like it is internally regulated, that black box on the rear looks to be the brush holder and regulator.
The voltages you quote are battery voltage, the alternator is not outputting.
Make sure the D+ connection is tight, that is the Charge Lamp lead.
If you have no joy, take the entire car to the place where the alternator was reconditioned and ask them to do a check of the charging system.
This should be a freebie.

_________________
Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Just take off the small wire for the charge light, tap a wire from your +ve battery post to that terminal on the alt, then put the wire back on.