VY commodore Check Alternator Warning went straight off again

[commygal]

Hi

Can anyone help I have a VY commodore had a stuffed battery took it in yesterday they replaced it with a brand new battery $250 later they tested Alternator before and after battery was replaced did a scan did a road test said Alternator is perfectly fine picked car up 5pm last night drove to work today everything was all good just before I got to work check alternator warning came up on dash then went off and didn't come back on but I was close to work turned car off and it turned back on just wondering can this happen if codes weren't removed properly as they did say codes didn't wipe straight away Im new to all this I rang mechanic back he said Alternator tested fine but battery needed replacing Im stressed and confused??

 

[wortus]

I haven't seen the warning, does it come up on the LCD display or is it a light on the dash somewhere?
The common failure of these alternators is the carbon brushes just wear out and the contact with the
slip rings on the rotor becomes intermittently faulty then eventually fails.
Disconnect your battery (neg terminal) and take the regulator out of the back of the alternator and check the length of the two carbon brushes
If they are worn your options are to replace the whole regulator or get new brushes soldered in, the later being a lot cheaper.

DON'T take the regulator out with the battery connected as it will spark if the +12V parts of the regulator touch the alternator housing.

You can also put a voltmeter across the battery terminals with the motor running and the voltage should be about 14.3 volts or around that
with a minimum of about 13.8 volts if the alternator is working properly.

 

[MYVESSV8]

regs are cheap at $40 with new brush's and takes 10 mins to do,

 

[wortus]

Last time I got an alternator light was in my VN and I just replaced the brushes because the reg was OK. That cost me $10 for a pair from a local auto electrician. Easy to solder in.

 

[MYVESSV8]

if they don't have access to a soldering iron etc was just saying, but agree brush's are cheap and easy, other possibility is the slip rings need cleaning too.

 

[edals]

I haven't seen the warning, does it come up on the LCD display or is it a light on the dash somewhere?
The common failure of these alternators is the carbon brushes just wear out and the contact with the
slip rings on the rotor becomes intermittently faulty then eventually fails.
Disconnect your battery (neg terminal) and take the regulator out of the back of the alternator and check the length of the two carbon brushes
If they are worn your options are to replace the whole regulator or get new brushes soldered in, the later being a lot cheaper.

DON'T take the regulator out with the battery connected as it will spark if the +12V parts of the regulator touch the alternator housing.

You can also put a voltmeter across the battery terminals with the motor running and the voltage should be about 14.3 volts or around that
with a minimum of about 13.8 volts if the alternator is working properly.

Yes, the Check Alternator displays on the LCD. Saw mine a few weeks ago after my belt shredded itself and fell off.
Also, if they don't have a volt meter, enter diagnostic mode to display voltage while running.