Possible Alternator Problem

I am trying to find the cause of a battery drain on my 2003 TD5 defender.

I have read a lot about a diode failure in the alternator as being a possible cause, but I am not sure how to test this?

I have removed the main cable from the alternator and this made no difference to the battery drain, however there is a small multiplug that plugs into the back of the alternator and I am having difficulty in getting to it to remove it to see if this could be causing the battery drain.

So what I need to know is if the alternator has a faulty diode, would the current drain back via the cables on the multiplug or the main alternator cable??

If it could be via the multiplug, any suggestions as to how to easily access it?

The size of the current drain is about 350mA if that makes any difference?

Unbolt alt , so not earthing , leave all cables connected and put ammeter in between alt body and earth , see if you have 350ma , if yes then thats where prob is HTSH

tacr2man said:

Unbolt alt , so not earthing , leave all cables connected and put ammeter in between alt body and earth , see if you have 350ma , if yes then thats where prob is HTSH

Click to expand...

Ok will give that a go.

Just need to work out how to physically get to it now as it is well buried into the engine bay.

Thanks

could it not just be a bust battery?

Dont rule out the starter motor either,internal shorting and all that jazz

BotswanaGuy said:

could it not just be a bust battery?

Click to expand...

No defo not battery, if the battery is disconnected it will hold its charge for weeks without dropping any charge .

another forum said:

Dont rule out the starter motor either,internal shorting and all that jazz

Click to expand...

OK, hadn't considered that...

tacr2man said:

Unbolt alt , so not earthing , leave all cables connected and put ammeter in between alt body and earth , see if you have 350ma , if yes then thats where prob is HTSH

Click to expand...

If I just take the big thick wire off the top of the alternator and place the ammeter probes between the alternator casing and the thick wire, will that not tell me the same thing??

Its just that will be a LOT easier to do as the alternator on a TD5 is buried deep in the engine

That will just tell you how many amps the wire can carry from the battery to the alt before it burns out .

You can remove the thick wire and put the probe between that wire and its terminal not the casing! Like wise with the other wires HTSH

tacr2man said:

That will just tell you how many amps the wire can carry from the battery to the alt before it burns out .

You can remove the thick wire and put the probe between that wire and its terminal not the casing! Like wise with the other wires HTSH

Click to expand...

Just as well I asked then!

1, charge the battery fully
2, put battery back in defender (if removed to charge)
3, reconnect wiring to battery
4, leave defender for 2-3 hrs
5, go outside to defender
6, open bonnet
7, feel the temperature of the alternator.................

If after a couple of hours the alternator is warm - thats where your current is draining to......

DEFENDER90-DAZ said:

1, charge the battery fully
2, put battery back in defender (if removed to charge)
3, reconnect wiring to battery
4, leave defender for 2-3 hrs
5, go outside to defender
6, open bonnet
7, feel the temperature of the alternator.................

If after a couple of hours the alternator is warm - thats where your current is draining to......

Click to expand...

OK cheers for that

DTd5 said:

OK cheers for that

Click to expand...

DTd5 - I realise that your post was many years ago but I am having issues with my own Td5 Defender, with which the engine cut out for no apparent reason yesterday after towing a small horse trailer for over an hour.

I have had issues with the battery in the resent spell of very cold weather and was about to replace with a higher grade unit. However, I spoke to a nearby auto electrician who seems sure that the alternator is the issue and needs to be re-built. He also said that there is a fuel cut out in the system which is actuated when the alternator fails.

Whilst this may well be the case, I thought that I would see what your win experiences are.

Many thanks in anticipation of your kind help. Alan