Disco 2 Alternator dead - reversed battery?

ldrego · Apr 25, 2020

Hi there all. I'm resurrecting my Landy after three years and made the mistake of reversing the polarity on my battery. How I managed to connect it up wrong , I don't know but I did. Two fuses blew, a 10 amp and a 40 amp plus the fuse that works the radio. I need to get one of those ordered up too I was wondering if I have blown the alternator or is there a fuse or relay that it goes through.
All help welcome.

ldrego · Apr 25, 2020

I've just tested my 100Amp link fuse and it is showing low resistance and good continuity. I notice that my radio is down but I have a blown radio fuse too. I will check all the fuses in the passenger side too tomorrow.

PopPops · Apr 26, 2020

ldrego said:
I've just tested my 100Amp link fuse and it is showing low resistance and good continuity. I notice that my radio is down but I have a blown radio fuse too. I will check all the fuses in the passenger side too tomorrow.

That is not good news. Either FL1 (150A in RAVE) will have blown to save the alternator, or the alternator will have "blown" to save FL1. There is no alternative, when the battery connections are reversed the diode pack in the alternator is "forward biassed" and will draw as much current as the battery can supply until something fails. It's worth checking F24 too.

PP

ldrego · Apr 26, 2020

Well that is good news as FL1 is alive and that costs £14! Lol. The good news is that I can now go and order a new alternator and see if that helps. F24 seems to be ok but I have 24 hours before i order anything so I am going to do a final check on the whole thing again prior to ordering.
Thanks for replying.
There was one thing though that I forgot to mention. The car has not been started for 3 years and hence I am thinking it is a possibility that the alternator has cables atttatched that may be heavily corroded.

Si Click · Apr 26, 2020

When this happened to my son's TD5 D90 the alternator was well and truly dead. Fortunately, once replaced there was no other damage.
Top tip for any other young driver changing their battery. Don't assume, check that the terminals of the new battery are on the same side as the one being replaced.

Nig43 · Apr 26, 2020

And the other giveaway is the size of the battery posts!!

ldrego · Apr 29, 2020

Nig43 said:
And the other giveaway is the size of the battery posts!!

Nothing a hammer can't solve.

Si Click · Apr 30, 2020

ldrego said:
Nothing a hammer can't solve.

I understand there was some non-percussive persuasion involved.

psk100 · May 28, 2024

Done the same after many long days working on upgrades on my disco 2 and yes its done the alternator so new one arrives tomorrow but also it appears more damage may have occurred so ordered a nanocom to try and sort but it may be possible screwed BCU as well as maybe the internal fuse board. Oh the fun caused by a tired brain not checking enough!

Disco 2 Alternator dead - reversed battery?

ldrego

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Si Click

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