No name 2 wire alternator

[Sparx]

The alternator on my perkins 4108 engine used to work fine. Then I started to tidy up the wiring. The alternator has only 2 terminals wired back to the panel through a cable. At the panel that are both connected together!

After fiddling around, the alternator now doesn't charge and the red light stays on permanently.

Can any one tell me the correct way to wire this up?

There is no name or markings on the alternator.

[Guest]

The alternator on my perkins 4108 engine used to work fine. Then I started to tidy up the wiring. The alternator has only 2 terminals wired back to the panel through a cable. At the panel that are both connected together!

After fiddling around, the alternator now doesn't charge and the red light stays on permanently.

Can any one tell me the correct way to wire this up?

There is no name or markings on the alternator.

No idea sorry, but a pic might help identify the alt.

[Tony Brooks]

I would expect an old 4-108 to either use a Lucas AC alternator but that has three or four wires or a Lucas ACR. ACRs could have just two wires (three terminal though) but one should run to the batteries and one from the warning lamp. This does not mean that someone has decided that the ignition switch positive terminal would be a good place to connect the charging lead but they would be wrong. There is no way both should be joined though.

 

As above - a photo please.

Edited August 11, 2016 by Tony Brooks

[Tiggs]

The alternator has only 2 terminals wired back to the panel through a cable. At the panel that are both connected together!

 

 

Then you have missed something.

 

Like another wire coming of somewhere else on the alternator?

Edited August 11, 2016 by Tiggs

[Sparx]

I hope this works

http://s1053.photobucket.com/user/Phil_Stranex/media/Mobile%20Uploads/20160807_164648_zpse36ta0ez.jpg.html?filters[user]=145034108&filters[recent]=1&sort=1&o=0

It a pic of the alternator. Difficult shot.

The puzzling thing is that it Was working.

[Iain_S]

I think you may have both wires on the B+ connection.

I'm no alternator expert, but it looks like an old Lucas ACR. If I remember correctly, the two spade terminals nearest the centre of the alternator are commoned, and connect to the battery.The (normal size) spade furthest from the centre is the field connection, which should go to the warning light.

 

Doesn't explain the warning lamp, though. I'd expect it to be out when the "ignition" is in the "run" position, as it would have +12V each side, and possibly on with "ignition off".

 

It looks like a mains cable has been used for the alternator connections. Heavier than necessary for the field connection, and possibly very much on the light side for the battery connection ! (Which raises the thought: was it wired using both cores of the mains cable for the battery connection, and has the field/warning light cable become detatched, and is possibly earthed somewhere?)

[Tony Brooks]

I confirm what Ian says above. It is a lather ACR and it looks as if both 9mm main charging output blades have somewhat undersized charging cables fitted to them. However there are two of them. These should run to the master switch (for strict BSS compliance).

 

As Ian says there does not seem to be a warning lamp cable fitted to the smaller 6mm blade and without that allowing the warning lamp current to energise the alternator it would not charge.

 

I know a very few of the earlier ACRs with the deep plastic cover were battery sensing and used one of the 9mm blades as the sense connection but thsi is exceptionally unlikely to apply here.

 

Rewire it properly.

[David Schweizer]

Sir Nibble is your man for this one, What he doesn't know about alternators could be written on the edge of a postage stamp.

[Tony Brooks]

If an ACR was charging and then stopped for more than an hour or so I very much doubt that it would self energise without the warning lamp connected - even if you rev the engine to maximum. If you stopped it in (say) a lock and restarted it then it might self energise if you revved it fast enough. There are some makes of alternator that will or are designed to energise without the warning lamp but the ACR is not one of them.