Thread: Alternator Failure?

You'll find a fair few alternator stories on here and Disco3.

Don't scrimp on the replacement though.

Originally Posted by tiojeffe

I think the alternator is shorted out internally or something. The mega fuse is still ok though.

LR stuffed-up the wiring for the alternator by attaching the B+ cable to the starter motor which needs a 500A fuse which means that a shorting alternator will not blow the fuse, flattening the battery and risking a fire instead.

Originally Posted by Graeme

LR stuffed-up the wiring for the alternator by attaching the B+ cable to the starter motor which needs a 500A fuse which means that a shorting alternator will not blow the fuse, flattening the battery and risking a fire instead.

Combining the alternator feed and the starter feed has the appearance of an elegant design.

Thanks to Graeme above, the light goes now on given that I had never before seen a vehicle alternator and starter wiring design where the conductors were common, (except on something where the alternator and starter were the same item.)

On vehicles I was used to, a thick conductor ran between the battery and starter and a second relatively thin one between the battery and alternator. In the case of the 3, while as I said, appearing to be an elegant looking design, I wondered if there was some major downside.

I had never thought about fusing of the alternator - that is major, and explains why a bad alternator seems to cause such unusual problems.

Is it still the same on the D4? I assume so. "Never say you are sorry."

Land Rover ......

Thanks,

Definitely dead alternator then?

I charged the battery, put it back in and when the battery terminals were put back on the voltage plummeted. Direct short I take it.

I have never seen anything like it though. It is the fact there is no fuse huh?

So is it hard to replace?

Graeme is the expert on this but the 500 amp fuse is probably OK.

It is so big it does not normally blow but instead allows the battery to be sucked dead as a result of an internal short in the alternator.

Internal shorts in an alternator are kind of a normal failure mode; a circuit design that allows the battery to be sucked dead is not.

In other words, as above, I expect the fuse is still good but the alternator, not.

The alternator is fairly easy to replace. The only difficult part is removing the viscous fan. You come in from the top behind the radiator.
A search on here will show up some examples.
They are pricey buggers though, I paid $430 when I did mine, since then they seem to be closer to $600.


http://www.aulro.com/afvb/d3-d4-rrs/173434-d3-alternator-replacement.html

http://www.aulro.com/afvb/d3-d4-rrs/...placement.html

http://www.disco3.co.uk/forum/topic54774.html

Same on the 3.0 in the D4! I haven't finished mine's conversion, with a 200A fuse (3.0 alternator rated at 180A) waiting for the separate cable to be installed. The delay is due to the 3.0's top radiator hose having to be removed and that I haven't yet worked out how to remove the top fan shield.

Ford Aust did a proper job of fitting a separate cable on the 2.7 in the Territory.

Yes why can't an inline fuse be installed at the connection of the cable to the alternator? Seems the logical fix - then again will an internal short blow a 200amp fuse?