Alternator - I have searched previous threads

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jamesgrant

New Member
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Hi all, how you doing?

So I have this lovely 1996 300Tdi, and my series landy is not used so much.

But this disco is complicated (for me), luxurious, but complicated.

I have searched and cannot find the answer, so here goes:

Thought battery was going on poor start up.
New(ish) battery installed (didn't have radio code, so had to be careful)
But with multi meter, engine running, getting 14V across terminals. BUT, rev the engine and voltage DROPS to 13.9V or less.

Now that shouldn't happen should it. I am having to charge battery each evening.So thought alterantor was duff.

Took disco to garage - they 'tested' alternator for free - said it was ok, but also said to feel alternator later and if it was warm, it could be discharging the battery. Well it hasn't felt warm - I am monitoring voltages as we speak - i.e. it is only 12.68V at rest and 3 hours later it is still 12.68 V (I know that is low - but that was after a 30min drive, not a charge from battery charger which is chucking in 14V at moment).

So, I suspect alternator is duff, but garage says no?

Now some of you guys strike me as more expert than the garage, what do you think?
(If you say alternator is gone, I have a few Ford ones of correct Amp-hour, which I can modify pulley to match disco pulley, but don't want to go to effort until sure the problem is alternator)

Cheers
 
How do James you ant got a brother called Foster have you?

Any how on the face of it the alternator does sound OK have you checked for a drain on the battery with the ignition off? There is a fred going on this in the Defender bit try a search.
 
I would agree that alternator seems fine and the battery still showing 12.68 V is fine . The battery is after all rated at 12V and while the voltage rises to 14 or so when engine is running and alternator charging it will drop back as soon as engine stops .
Starter is designed to operate on 12V and will work fine with that voltage ,
I've had 2 Discovery 300Tdi's (both 96)and one of them was a very 'lazy' starter - it turned over very slowly but always started . I thought when frosty weather came it wouldn't have a hope of starting - but it did every time .
My sister has a 98 300 Tdi at the moment and it's the same way but always starts .
By poor start up I take it that the Disco starts but the slow turning of the engine makes you think there is a problem .
As battery and alternator seem fine I would suggest it's just a characteristic of a lot of Disco 300 Tdi's .
I've read a few posts on other forums where owners were concerned by the slow turning and many reported that their own were the same - but they always started .
Hope this helps .
 
As Dooroy said, the charging circuit sounds right. It shouldnt go above 14.2 but even with everything on is still putting back more than is used. Plus the Diesel unlike petrol engines, doesnt need power to keep it running.
What made you check the alternator? If its not starting well do you mean turning over slowly or not firing up as soon? Might be glow plugs if its cranking more and more or as previously said sticky starter motor. Check the wiring to the starter as well as if the power lead to it is lose then it will give a higher resistance/less power on cranking.
 
Had my alternator die on me a couple of years ago - batterly light stays lit even after turning ignition off. I don't think this is your problem, or even if there is a problem, otherwise your battery would go flat pretty quickly.

Mine (200tdi) wouldn't run with no charge in the battery with broken alternator which I wouldn't have expected it to. If you jumped started it, it would cut out about 10 seconds after disconnecting the donor battery.
 
No, when I say trouble starting, I mean on cold days, it WON'T start.

Had to jump start it the other day, hence charging every night until I figure out which part to tackle first.

Guess I'll check the battery drain idea (once I've figured a way of getting the radio code)

Cheers anyway
 
Check the voltage acros the terminals at night last thing, then again before you atempt a start in the morning.

If the voltage has dropped, there is your answer. If the voltage is marginal but it still wont start, then you have lost the cranking capacity in the battery, especially affected by cold weather.

Sounds like your alternator is working fine. When you get a problem like this, dont use secondhand batteries unless you are tasking from a source you know works, ie: borrow one off another disco that works to test it, then go and buy a decent one.

More people mis diagnose problems through using duff replacements than you can imagine. same for alternator, dont **** about modifying one, go and get the proper one. They are as cheap as chips if you go to a factors.

Have you checked out your starter motor?

These can be affected by cold to you know.

OM
 
Got a brand new battery from a mate to borrow for a while (off a Range rover).

Can get radio code from dealership for free (Yippee)

Will shove the new one on and see if voltage drops over night.

If it does I'll fit a new alternator (how cheap do you call chips?)

If it is £60ish - that is maybe worth it and will save me the time of modifying - but if more like £120 I'll modify and get a bit better with lathe and milling machine etc.

Thanks for all replies, great forum you've got here.
 
jamesgrant said:
Got a brand new battery from a mate to borrow for a while (off a Range rover).

Can get radio code from dealership for free (Yippee)

Will shove the new one on and see if voltage drops over night.

If it does I'll fit a new alternator (how cheap do you call chips?)

If it is £60ish - that is maybe worth it and will save me the time of modifying - but if more like £120 I'll modify and get a bit better with lathe and milling machine etc.

Thanks for all replies, great forum you've got here.
Click to expand...
I tried lucas service motor factors and they wanted 168 quid and my old alternator. Fixed it myself thankfully. Recon units are advertised in the mags for 60-80 quidish.
 
You will find a auto electrician who can rebuild it for about £45/50 if your lucky - look in industrial estates and down side streets and you will find someone who will be reasonable.
 
Thanks for all replies and links etc.

In case this helps anyone else, I think the poster who said that the started motor could be on its way out is closest .

Reason?

New battery now on. 12.7plus Voltsnight and morning. Even though engine now starting, it is sluggish when cold and I can here the battery having trouble, hence sounds like starter motor is needing more juice than when warm. Or solenoid? but I know nothing about those either.

Anyway, I have a way forward now.
 
Does that mean i get a prize for helping you......................na, ah well..............merry christmas and a hapy new starter!

OM
 
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