VR Commodore, changed alternator but still not charging

[Deff]

I'm lost for ideas, changed alternator and it charged for first 2 starts but nothing after that, surely a 2nd alt hasn't failed?

Any ideas?

[immortality]

there is a wire that runs from the alternator to the battery to sense voltage. if this wire is broken it will not charge. at the battery this single wire has it's own connection and plug from memory

[Deff]

Hey mate,
Yeh that wire is hooked up, pulled alt out again and checked everything was good, it's a recon unit so should be fine. Put back in and it's charging off and on now but the sense wire is not broken or dodgy in any way so completely stumped

The main wire is in new like condition so no corrosion etc..

[darcycammo]

i have the same problem aswell

[BlackVXGTS]

Pull out the voltage regulator and make sure they have replaced the bushes properly during the recon.

darcycammo, this may be the answer for your problem. The bushes wear down over time and need to be replaced. You should be able to replace the voltage regulator without removing the alternator.

[Deff]

Checked all that, it all seems ok.

If car is not charging when switched on a good hard rev will put the alt light out so I'm confused even more, once it goes out it seems to stay out it's just that sometimes it will stay on unless revved hard if that makes sense.

[hako]

To check if it is indeed the brushes in the alternator sticking, simply start the engine and presuming the red light is on, tap the rear of the alternator (and the black reg) with either a soft faced hammer or the handle of a screwdriver - this will usually jar the brushes into contact with the slip rings - then if the red light goes out you know it is the brushes sticking.
90% of 'reconditioned' alternators simply are fixed and then painted - either brushes or a bearing will have failed and parts involved cost under $10, so a reco alt is generally just a repaired alt.

[wamboin23]

if its not turning out the light unless it is revved hard, sounds like it the alternator itself, I'd take it back and get them to test it. could be a regulator problem, or diodes.

[Deff]

Cheers guys, one last question. Is there anyway to test the reg while it's off the alt?

[delcowizzid]

before checking the reg get a multimeter and check that both wires that plug into the reg have 12v with the key on when unplugged from the alternator white one goes directly to the battery via a fusable link the other brown one goes to the batt light both should have power with ignition on