19 replies to this topic

[gaspen]

Hello

 

It is a 998 with Lucas 16ACR alternator. I restored the Mini in 2018-19, the alternator was refreshed too : new bearings, regulator, connectors....

 

The weekend trip from home to our destination was uneventful. The symptom which occured  when we left for home. 

 

 

1) Switched to IGN > IGN light was OFF 

 

2) After 1 or 2 on/off the IGN light came alive

 

3) Starting the engine, at idle there is no charge, the ignition light is ON (I can live with that)

 

4) When I drove the car the ignition ligth was still ON

 

5) I stopped the car and I had to increase the RPM to pretty high value to get charge and to IGN ligth go OFF

 

6) Back to idle and after ~10 seconds > IGN light ON

 

7) We started our journey home prepared for a battery exchange but there wasn't any more issue

 

 

 

What should I check ?

[68+86auto]

disconnect the small alternator terminal and connect the wire to ground and see if the light comes on with the ignition reliably (without starting the engine).

[alpder]

And the negative of the above test too... i.e. check that the light reliably does NOT light when disconnected from the alternator (and disconnected from ground): maybe there is an intermittent short of the wire to ground, possibly being made/broken by the vibration of the engine.

Edited by alpder, 30 October 2024 - 08:34 AM.

[gaspen]

The IGN light is ON when I earth the  brown/yellow wire at the alternator

 

I have battery voltage (~12,4V) on the alternator terminals

 

There is no charge on idle or even on higher rev

[alpder]

I've taken apart a lot of alternators (to make motors - but that's another story). But I remember that on many alternators there are some screws which hold the plastic cover on the back, and then two more screws which hold the brush pack (usually with combined regulator) onto the body. Those brush-pack screws also serve to ground the brush-pack. If they are loose or corroded then the alternator won't work correctly. Worth checking, perhaps?

 

Also, on some older Lucas alternators the regulator is a separate module inside the cover, with three or four wires coming from it. Again, if it's that type then worth checking the wires are securely fitted without corrosion.

 

Finally, of course, could be a dying regulator and/or worn-out brushes or a completely worn-away slip-ring. Regulator and brushes are usually replaceable but worn slip-rings generally aren't.

 

by the way when working on the alternator remember that the main cable is connected direct to the battery without a switch and without a fuse. Best to remove the ground wire from the battery before working.

Edited by alpder, 30 October 2024 - 05:50 PM.

[68+86auto]

I had a quick look online for a service manual and all I found didn't say more than has already been said. I expected to find how to bypass the regulator.

 

Start by checking the brushes and slip rings, make sure the brushes are moving freely. It does look like the 16ACR slip rings can be replaced.

 

 

I have some universal alternator testing instructions that I'll find and upload.

[mad4classics]

Aswell as the above could be a diode gone in the rectifier stack. Slip rings are replaceable.

There is a complete PDF of the Lucas Workshop Manual Vol 3 on the Land Rover Series One Club forum.



https://www.lrsoc.co...orkshop-manual/

You want section A5 in the first chunk.

If, like me, you're interested in Alternator workings there's an interesting write up on this web site; scroll down to "HISTORICAL LUCAS ALTERNATOR REGULATOR AND IGNITION DESIGNS"

https://www.worldphaco.com/

Edited by mad4classics, 31 October 2024 - 08:20 AM.

[gaspen]

Thanks all of you

 

I'll will check the belt first.  If the belt won't help I'll start examine the alternator.

 

When I restored the car I've taken out the whole loom from the car. I've replaced all terminals and all wires that was broken. So I believe the loom is okay. 

[gaspen]

Another question : is there any guide about the wire sizes used in Minis ?

 

For example there is a brown and a brown/blue wire from the alternator to the solenoid 

 

What should be their gauge / area ?

[68+86auto]

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It looks like there's a few different regulator types which will have slightly different bypass procedures.

 

The landrover manual that mad4classics linked has all the required details. It is under bench testing but could be done in the car.

Edited by 68+86auto, 31 October 2024 - 01:14 PM.

[gaspen]

Look dad what I found ! 

 

 20241031_162302.jpg   29.58K   4 downloads

[gaspen]

I've noticed that there is one small copper plate inserted into the brushe's hole, but only one

 

Should it be in both holes? It looks like I've lost one ?

 

 20241101_131638.jpg   29.55K   2 downloads

 

[mad4classics]

I've noticed that there is one small copper plate inserted into the brushe's hole, but only one

Should it be in both holes? It looks like I've lost one ?

20241101_131638.jpg

No, it's only in one; a genuine Lucas brush set used to contain a single replacement clip.

[gaspen]

I'm waiting for the new brush set so I check what I can check on the alternator.

 

The Rectifier

 

I learnt that all 9 diodes should allow the voltage to flow only for one direction. I've measured them with a multimeter switched to diode test. 

 

Diodes in circuit 2 and 3 are all the same (where the outputs are)  but circuit 1 flows in the opposite direction 

 

Is it the normal operation ?

 

 20241103_095820.jpg   33.12K   0 downloads

[68+86auto]

I'm waiting for the new brush set so I check what I can check on the alternator.
 
The Rectifier
 
I learnt that all 9 diodes should allow the voltage to flow only for one direction. I've measured them with a multimeter switched to diode test. 
 
Diodes in circuit 2 and 3 are all the same (where the outputs are)  but circuit 1 flows in the opposite direction 
 
Is it the normal operation ?
 
20241103_095820.jpg

I'd need to look at one and a diagram to be sure but I guess it is fine.


If it's an original rectifier assembly then that should be fine, a diode wouldn't fail and reverse it's direction as far as I'm aware. If the readings are the same as the others but reversed, I say it's fine.

If it's a replacement part, who knows.