Disco 2 Alternator causing a parasitic bleed?

My battery goes flat as a brick if i don't use the Disco for more than a week. Lately i've just been removing a lead when not using it but was chatting to a couple of guys who both suggested it would be the alternator at fault. They did say what the fault was but i neither remember or understood...
They said to disconnect it for a week and see if it then starts. A good idea but since we spoke i've been using it so it hasn't been an issue
Is this a known / common fault?
When i mentioned it to my mechanic he had never heard of this happening

Alternator causing parasitic drain is not uncommom at all

Diode going to earth, replace with new / rebuilt alternator,
Normally get a slight glow from the batt light when switch off, very common fault,

Great! So much easier to to throw a new alternator on it than mess about with a multimeter!
Pity it's not the same as the one on my 300TDi. That one's only about 18 months old and sat doing nothing while i decide what to do with it

yfo866 said:

Great! So much easier to to throw a new alternator on it than mess about with a multimeter!

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Though you should mess a bit with the multimeter before throwing in a new alternator otherwise how would you know that the alternator is causing the drain unless you disconnected the alternator and got rid of the drain.

yfo866 said:

Great! So much easier to to throw a new alternator on it than mess about with a multimeter!
Pity it's not the same as the one on my 300TDi. That one's only about 18 months old and sat doing nothing while i decide what to do with it

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Easier still to replace the rectifier - probably less than a tenner too

sierrafery said:

Though you should mess a bit with the multimeter before throwing in a new alternator otherwise how would you know that the alternator is causing the drain unless you disconnected the alternator and got rid of the drain.

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I'll disconnect it for a week first to see if the battery is dead or not. If it is, it isn't the alternator, if it isn't, it's getting a new one.
One isn't a total muppet!
No comment regarding being a partial one though...

Disco1BFG said:

Easier still to replace the rectifier - probably less than a tenner too

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That's as maybe, but considering i know buggerall about what a rectifier is, what it does, where it sits, how to establish if it's buggered and which one to get to replace it, it's probably best all round if i just put a new alternator on...
I can then put the old one into stores for when i kill the new one due to my attraction to deep water
Starter motors and alternators generally last about three years on my Landies

yfo866 said:

That's as maybe, but considering i know buggerall about what a rectifier is, what it does, where it sits, how to establish if it's buggered and which one to get to replace it

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Ok - there are vids on the tube of you which explain all that, and how to fit a new one too

Disco1BFG said:

Ok - there are vids on the tube of you which explain all that, and how to fit a new one too

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Took your advice, watched a video, now know what it does, not sure where it is as the guy was using a Toyota alternator, and then found a rectifier for £17.50. Looks easy enough to replace as it's all on one 'plate'. I won't be able to leave it for a week for the time being as i have about fifteen jobs to do this week and will be moving it back and forth. Sump guard, new exhaust, centre console out, replace both back doors glass and motors and whatever else is missing inside. It's an ex commercial and they don't open or let any light through. Wheel spacers, tighten steering box, full service, replace all fluids, fit wading kit, wire in the led light bar it came with.

Found another video, this time a very nice man (Sleepy Cat Pictures) is swapping the rectifier in a TD5 alternator.



It looks like it's been sprayed in oil from the engine. Really mucky inside. Would you have given it a quick wipe with a rag or attacked it with brake cleaner or something similar?

And what if the winding is shot ?

sierrafery said:

And what if the winding is shot ?

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Well, this is why I liked your post #5, above .....

sierrafery said:

And what if the winding is shot ?

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What now?
I've just about grasped what the rectifier does...

It was a rhetorical question... if you dont have the skills to check what's wrong with the alternator simply replace the whole unit cos if it has the winding shot you will change the rectifier in vain ... to change the rectifier you must do some troubleshooting first to confirm it's that and not something else if you see what i mean

sierrafery said:

It was a rhetorical question... if you dont have the skills to check what's wrong with the alternator simply replace the whole unit cos if it has the winding shot you will change the rectifier in vain ... to change the rectifier you must do some troubleshooting first to confirm it's that and not something else if you see what i mean

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I do but everybody seems to be telling me, "mate, it's ya rectifier..." Would shot windings cause my electric to dribble out?

Why would anyone replace an existing rectifier without proving its faulty first

discool said:

Why would anyone replace an existing rectifier without proving its faulty first

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Well... When i get time, i'll disconnect the alternator to see if it's at fault. If it is, then i'll replace the rectifier. If that doesn't fix it then i'll replace the alternator and gain a spare rectifier. Alternators and starter motors don't last more than about three years on my Landies anyway.

Had a new alternator and starter motor and serpentine belt fitted a couple of weeks ago. Battery has been good ever since. So it must have been the alternator!