300tdi alt

This is one of those Disco/Defender questions that your never sure where to post.

Anyway - 300tdi Disco engine in my 90 needs an alt I think, last night after a long drive on the motorway lights on full, heater etc I noticed the lights looked a bit dim. I was knackered it had been a long day and it didn't cross my mind that the alt was buggered.

After a jump start from a friend I got it going - drove home and on returning home the lights were almost out the battery was drained so much.

No charge fault light in sight (it works).

So probably the regulator? Can you change these or is it just the diode packs you change? Is it worth it.

Also, do I need to fit a Disco alt? Will any of the Defender ones fit?

You have checked the belt tension? Although you should see a low charge warning.

oh yeah - and the charge light only comes on when the belt snaps, not when its not charging. Stupid poxy design...

Update: last night I charged the battery for about 8 hours and this morning the engine started on the key first time - no bother.

Great - so I drive to work keeping electrics use to a minimum. Got into the car tonight, it wasn't as sharp but she started none the less and I came home with sidelights only - I turned the interior light on to try and gauge my battery and as if by magic its nice and bright, so I bring on the headlights the light dipped for a millisecond as you would expect to see when the voltage regulator steps up the output slightly. I put the blower on full, no change to the lights everything nice and bright.

Get all the way home park it on a hill (incase) and turn it off. NO WAY was it going to restart - It would have been lucky if it even moved one piston through a full stroke.

Roll it down the hill she starts no bother - again lights nice and bright.

Park it at the front of the house and tried starting it again - no go.

SO I suspect now its an earth harness or maybe the 2.5NA starter feed is not up to it. I am still confused by last night though because after 40mins driving with the lights steadily dimming they were nearly out when I got home. That in my book points to an alternator fault making me think it ran all the way home on battery only.

I am going to let the engine cool till about 11 tonight then try starting it - if it starts then the starting issue is related to a warm engine - because so far every time its not started has been on a hot engine.

I don't suspect the battery as its about a year old and was working fine up until the last moments of its 2.5NA days.

Does anyone know the recommened battery amerage for a 300tdi, and what does the starter draw 150amps ish?

Yeah your right Boydy the light seems to do FECK ALL - the 300 disco alt died and the only warning was the lack of tacho!

Reet... The starter will draw about 500-700 amps, they are ****in huge! The wiring, if its good, should be more than good enough, the new starter actually has less work to do. I am certain this is alternator related. Take a voltmeter to the BATTERY terminals, read the voltage, read the voltage with the engine at tickover, and then again with it at about 2-3000 rpm.

Check the light bulb in the dash, does it come on with the engine stopped? As i said, if this circuit fails then the alternator dnt charge.

dodgy earth

I THINK - its fixed.

Boydy your a genius!

You said something that stuck in my head when I went out to try starting it again about the charge light, now I remember this gives the stator charge to start the cycle. Last night I had taken the charge wire from the spade and put a ring on it and put it on the stud. I WRONGLY assumed that they would have at least put the BIG wire on the BIG stuf marked B+!

WRONG - So last night before I started it was connected like so:

Main battery wire to the Charge light circuit.
Charge light circuit to the tacho
and nothing to the B+ power out stud!

I then effectivly moved the charge light wire to B+ (working in the dark I made assumptions) and the battery main was still connected to the charge light circuit.

So I have just swapped them both, so I will confirm that the main battery cable is now on the BIG stud marked B+.

The battery is flat so can't really test it yet but the charge light came on nice and bright so I will charge the battery till 11ish and try starting it and see what happens.

The next question is will this have caused any damage to the alt, charging circuit etc? Will the fact that the alt was connected incorectly have let the battery drain via the alt all day?

It also means that my battery must just have had enough power in it to run my headlights on the way home tonight and it wasn't the alt working - impossible for it to have been I guess.

OK I didn't do the 11PM check -didn't see any point and I couldn't be bothered.

This morning, after about 16hours charging the charger was down to about 1 amp charge rate. Put it in and she started no bother - with the cab light on as a gauge of the alt coming on I started the engine and the light got noticably brighter.

I think thats the alt problem dealt with - I will see how it is on the way home tonight and I will see if she restarts once I get there - I think it will.

I hope the battery was not thrashed with all the draining and no charging.