replacing alternator brushes

[jasper5]

Just realised what your intentions are...repairing a duff alternator...you might find that the rectifier is your problem rather than bushes, it could also be other things.

[steve_earwig]

Burnt comutator, disconnected or short-circuit windings etc. etc. etc. but, in these days were everyone chucks it in the bin, it's still laudable to have a go.

[jasper5]

Burnt comutator, disconnected or short-circuit windings etc. etc. etc. but, in these days were everyone chucks it in the bin, it's still laudable to have a go.

I know that, Steve, that's why I tried to help last night....I would have put him onto my mate who has a business reconditioning alternators and starters but didn't get time today.

I'm beginning to wonder if i'm coming across as confrontational sometimes, when my sole purpose is to help people.
I know I don't have a sparkling personality, but though my heart is somewhat damaged, it's still in the right place.

[teamster1975]

I know that, Steve, that's why I tried to help last night....I would have put him onto my mate who has a business reconditioning alternators and starters but didn't get time today.

I'm beginning to wonder if i'm coming across as confrontational sometimes, when my sole purpose is to help people.
I know I don't have a sparkling personality, but though my heart is somewhat damaged, it's still in the right place.

Steve wasn't having a pop at you jasper! You know what it's like on here with the banter, and written word never comes across the same as a chat in the pub
Which reminds me, I have no beer in the house!!

[steve_earwig]

I think I'm a bit guilty there, I tend to think of a huge wordy sentence then chop it down so it actually makes sense, but I think in that case perhaps it was lost. Sorries!

[millard]

no worries at all guys. I'm just very grateful to you all for taking the time to reply and try to help me out here, no need to apologise.
I realised that the original part no for the alternator is not what I stated before but 0124615002. The previous number I gave was for a reconditioned unit and must have been the stock number from the recon company.
Also just realised that it's likely that the brushes will come together in a small unit which includes the regulator. Been quoted around £45 for one but I can get a used unit with 28 day warranty for less so if I can't come up with a better price I'll not persue it any further.

[millard]

I got the old alternator off and I have the replacement on the bench.
Still looking for brushes etc but then noticed that the brushes on the old unit were actually OK, maybe the rectifrier then?
So I stuck it in the vice and rigged a Torx50 into my DeWALT battery drill and whizzed it round at around 1700rpm - voltmeter across the terminals, nothing, as expected.
Then I did the same with the replacement - same result,,,bugga. Then I thought - wait a minute, maybe I should be reading from the heavier terminal to the chasis (earth?), still nothing. Same from the chasis to the small terminal.
Is this the way to read an alternator when it's running on the engine?
Am I doing something stoopid? or is my replacement a dud as well?
cheers
Millard

[teamster1975]

Good idea that millard! I've done a bit of googling and apparently you need to put a load across it in order to get a reading, otherwise you can damage the reg/rec.

[steve_earwig]

It needs a 12 volt battery across it to work pwopperly.

[millard]

I'm a bit thick on this fellas, help me out please - I need a simple explanation that a bright five year old would understand, don't want to fry the bluddy thing. Which connection has what attached to it? and where to I stick the leads from my meter?
thanks

[steve_earwig]

It needs 12 volts to power the field coils. There's no magnets in it so if it's spinning around not energised it won't generate any power. Well, not much anyway (earth's magnetic field and all that). It really needs connecting like it is in the car.

[steve_earwig]

I have a book on it somewhere, if you want a proper explanation. Mind you, it's a Haynes so it could be anything.

[millard]

Thanks Steve.
I've rebuilt old Lucas 6v dynamos and their mating magnetos successfully in the past but I had a very good book with step by step explanations and drawings to follow. What I need if you have the time and inclination please is something like this - "stick the positive lead from your battery to the large (or small ) screw terminal and the negative to Small (or large ) then put the voltmeter leads here and here etc etc".
I eventually got the hang of the old Lucas stuff but alternators are a bluddy mystery and a black art, I think I need an alchemist

[millard]

Just been trying to think this through, tell me if I'm right please.
When hooked up on the car am I right in thinking that the small screw terminal takes a 12v lead from battery via ign sw to energise the field coils?
Neg from battery goes via chasis earth connection to alternator body?
The large screw term stuffs power back up the batterie's jacksie when it needs it?
So when on the bench if I connect 12v Pos to the small term and Neg to the body, then whiz it round with my DeWALT I should read it's output if I put the meter accross the large term and the body?

[teamster1975]

So when on the bench if I connect 12v Pos to the small term and Neg to the body, then whiz it round with my DeWALT I should read it's output if I put the meter accross the large term and the body?

Sounds about right