Disco 1 Alternator does not charge, warning light does not come on

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tomke92z said:
I checked the earths, they all are ok.

I took off the heat cover and got a better look at the alternator. I noticed that the one white wire which was hanging is coming out of the D+ slot so I figured this is where the yellow-brown wire should be connected.
uc

I connected it as in the picture below but the warning light still does not come on when ignition is on...
uc

Is there any fuse that could be broken? Or any other switch or whatever that could be faulty between the alternator and the dashboard? Or it has to be the warning light itself?
Click to expand...

See the silver brush box, see the dirty off white round connector partially hidden, see the black stub the connector should be pushed on to?
 
lynall said:
See the silver brush box, see the dirty off white round connector partially hidden, see the black stub the connector should be pushed on to?
Click to expand...
So the brushes are under the silver cover with 3 bolts? I was wondering what's there. Sorry for my ignorance - I would really love to know more about car mechanics and electronics but there is still a long way ahead of me... :) I checked the wires which are outside, the voltage is there, connection to the ground is ok.

sierrafery said:
Did you try to connect the NY wire directly to earth to see if the light works that way or not?
Click to expand...
With ignition on just connect the wire to alternator's body or engine and the light should come on?

I'm leaving today for a couple of days. I will get back to the topic after the weekend. Thank you so much for all your support so far, I really appreciate it! And I really enjoy checking all of this and getting to know my Disco better :D I love how simple this car is!
 
One more thing. Yesterday I noticed that the clock is slow. It's working but it's not showing the right time. And fuse nr 14 is the one responsible for, among others, the clock. I will have to take a look at the fuse box and the wires below the steering wheel. The thing is that I have some additional lights, a CB radio and other stuff connected by previous owners and there is a real mess around the fuse box. So there might be some problem there.
 
tomke92z said:
So the brushes are under the silver cover with 3 bolts? I was wondering what's there. Sorry for my ignorance - I would really love to know more about car mechanics and electronics but there is still a long way ahead of me... :) I checked the wires which are outside, the voltage is there, connection to the ground is ok.


!
Click to expand...

Yes the silver bit is the brush box, i call it brush box but it is actually the reg pack, remove three bolts and gently wiggle the box out, and you will see the wire I mentioned.
Refit carefully so as not to damage the brushes and do not overtighten them three screws.

Look on ebay for a127 brush box.
One of many, brushes are held in by the little steel pin, dont worry they cannot make a break for freedom once pin released, just stops them being damaged in transit.

https://www.ebay.co.uk/itm/18314337...0jADPJ60PAmI03PYc5lpKnXij/|tkp:Bk9SR5r1-KrCYQ
 
sierrafery said:
Yes, it should
Click to expand...

I did the test. And yes, the light came on! So the bulb is fine. Now why doesn't it come on normally?

I also did a test of the diode pack as explained in the film below (starting at around 5:30). This tests whether the current flows in just one direction. In my case I did not disconnect the wires from the alternator but the battery was disconnected from the car so I guess I should obtain the same result (no voltage at the alternator other than that from the multimeter).



What I observed is that I got around 720 mV in one configuration (this is fine as the guy says it should be 500-800 mV) BUT when I switched plus with minus I did not get a null reading - I got a positive value which was constantly increasing up to 2000 mV when the multimeter stopped displaying anything. I understand this proves that my diode pack is faulty and I need to take the alternator out and replace the diode pack? This is probably the reason why the alternator does not get excited? And can this be the reason for the light coming on when I ground the green-brown wire but not coming on on its own? Or is this unrelated?
 
If the warning lamp doesnt come on with the wire connected to the alternator's proper terminal for that there can be a winding issue, IMO you better get a new alternator cos your's seems fubar for good not just the rectifier
 
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^^2 what he said alternator needs replacing, voltage regulator is fried probably from the terminal "floating" for a long time.
 
If you find a decent specialist he will test it for you and only replace what needs to be replaced. He'll also clean up the commutator and replace the brushes. I am lucky enough to have a bloke like this who works out of his domestic garage, nearby. Family business. Very good prices and he can handle rare stuff like a starter motor for a semi-auto air-cooled VW beetle. No NOS or anything else could be found.
Best of luck!:):):)
 
I can take it to a specialist but I was really hoping to do it by myself... Just for satisfaction :) I took out the alternator and opened it. I was pretty sure I have a Lucas alternator but turned out its Magneti Marelli. But it looks exactly like Lucas A127-65. Both producers did identical alternators for Discoveries?

uc


I noticed one thing. Maybe it's normal but it's always worth to ask... The winding is broken on one side:

uc

There is a nice connection on the other side:
uc

Something tells me that this might not be right :)

BTW. I will buy another alternator anyway. I want at least 100A as I will mount a winch. But I want to have a working spare alternator anyway, that's why it would be nice to fix this one.
 
Glad you found the (now obvious) break.
Now you can repair it to have a cheap spare when you then spend your money on the one you really want.;)
 
tomke92z said:
True, that's the plan. I will solder the wire and let you know if it's charging now :)
Click to expand...
And although I respect totally what @sierrafery knows about electronics, I have yet to see an alternator of any reasonable age that isn't black inside. I think it is just general dirt and carbon from the brushes. Ditto starter motors!;);)

But I'd still check the diode pack to make sure it's ok.
;););)
 
tomke92z said:
Just one question out of curiosity. How could the winding break just like that? I guess it was soldered poorly?
Click to expand...
It's possible that some wires got short circuit through the winding's insulation hence the current was higher and that joint was weak so it blew like a fuse..... that winding doesnt look OK at to me
Stanleysteamer said:
I have yet to see an alternator of any reasonable age that isn't black inside.
Click to expand...
they are black inside but the windings should not look like they passed through fire IMO.... here's a more than 15 years old one dismantled and the winding's colour is visible in the image from the video in post 27 too and it dosnt seem a new one to me
upload_2023-2-5_21-8-39.jpeg
 
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