Disco 4 (LR4) Charging system fault

Afternoon all. So today on way to work my disco 4 has developed a new fault. So with engine off the voltage shows 12.3v. She starts perfect and voltage jumps to 14v, after approx ten seconds the dashboard beeps (displays charging system fault) and immediately the voltage drops to 13.5v.

Currently on 149k miles, alternator changed at 118k and recently had new battery and starter motor 2 months ago. Today is first time this has happened.

Regards

Ben

Hi, first of all check if the battery clamps are well tightened

Also charge the battery up with a marine charger before trying to diagnose any further.
How old is the battery? Has it been tested?

kermit_rr said:

Also charge the battery up with a marine charger before trying to diagnose any further.
How old is the battery? Has it been tested?

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Brand new Kuasa AGM battery

benh999 said:

Brand new Kuasa AGM battery

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Has it been fully charged before you started?

kermit_rr said:

Has it been fully charged before you started?

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Yes

benh999 said:

Yes

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12.3v is pretty much flat.
13.5v isn't low enough to cause a low charge scenario
Above i said marine charger, i meant mains. That's auto correct for you!
It would be worth charging again, then starting and monitoring the voltage at the battery.
Check you can't move the terminals at all on the battery, if they slip even a bit then take them off, open the gap some more and reattach.

kermit_rr said:

12.3v is pretty much flat.
13.5v isn't low enough to cause a low charge scenario
Above i said marine charger, i meant mains. That's auto correct for you!
It would be worth charging again, then starting and monitoring the voltage at the battery.
Check you can't move the terminals at all on the battery, if they slip even a bit then take them off, open the gap some more and reattach.

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Thanks, I’ll drop the mains charger oh her tonight and will check all terminals..

What’s throwing me is she’s charging at 14v but after approx ten seconds the fault appears on the dash and the charging voltage drops to 13.5v

benh999 said:

Thanks, I’ll drop the mains charger oh her tonight and will check all terminals..

What’s throwing me is she’s charging at 14v but after approx ten seconds the fault appears on the dash and the charging voltage drops to 13.5v

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Could be unrelated. Modern cars charge in funky ways. Mine doesn't charge at first startup but doesn't throw an error either

Plus 1, Also check the earth cables as there are reports of them failing , particularly one hidden behind the front wheel arch liner , OSF

if that all checks out after testing it would get it plugged into a decent diagnostics as the later models have a lot of electronics, did the BMS module get reset after fitting the new battery plse

With it plugged in u can also monitor the live data which is very useful for diagnosing errors , plus do u happen to know what make alternator was changed as that’s very important, thks

hope that also helps

Update….. she’s booked in to be
checked over however things have changed since yesterday. So yesterday you would star car and get 14v straight away until the warning light appeared and voltage would drop to 13.5v. Now when I start her randomly the alternator doesn’t start to charge until the “Charging system fault” light comes on. At this point it jumps up to 13.5v.

Then……… when driving it gets weirder, on a couple of occasions the fault message/battery light disappeared, when this happened the alternator stopped charging and 12v was displayed, as soon as the fault message reappeared on the dash the alternator charged to 13.5v

Very very strange however I’m assuming my altenator is on its way out

Yes that's not right. You shouldn't see anywhere near 24v. I think 18v is the max on some smart alternators

Sorru

kermit_rr said:

Yes that's not right. You shouldn't see anywhere near 24v. I think 18v is the max on some smart alternators

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benh999 said:

Sorru

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kermit_rr said:

Yes that's not right. You shouldn't see anywhere near 24v. I think 18v is the max on some smart alternators

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Sorry that should have been 14v (fat fingers)

Still very strange. I wonder if the BMS was reset when you got a new battery?

kermit_rr said:

Still very strange. I wonder if the BMS was reset when you got a new battery?

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Well she’s booked in now so one way or the other she will be sorted when I get her back

kermit_rr said:

Could be unrelated. Modern cars charge in funky ways. Mine doesn't charge at first startup but doesn't throw an error either

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She’s not been in the garage yet to be fixed how mine has started doing this.. when you start her the alternator is not charging at all. Once the “charging system” fault appears after 10seconds it begins to charge but only at 13.4 volts

benh999 said:

She’s not been in the garage yet to be fixed how mine has started doing this.. when you start her the alternator is not charging at all. Once the “charging system” fault appears after 10seconds it begins to charge but only at 13.4 volts

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My l322 didn't always start to charge immediately, i think it has a soft start 'feature'

So we have solved the “charging system fault” message on the dashboard..

My mechanics words were :-

The charging fault was a corroded wire in the plenum that provides the power to the battery monitor sensor

So if anyone else is having this message this is worth a look

Thanks for letting everyone know and glad you got sorted