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Disco electrical problem

alan drover

alan drover

In Fourth Gear
Can anyone help, please? I have owned a '94 Disco 300 for about 6 weeks now which has an intermittent electrical fault. The vehicle had a new (reconditioned?) alternator fitted 2 months before I bought it by the previous owner, because of bearing failure of the original. (Engine has done 95,000). I'll describe the fault.

If you switch the ignition on from cold, or after being stopped for 1/2 hour or so, everything's fine. If you have run for say 10 miles then switch off and on again, two things happen: 1. The charge light does not come on and 2. The rev counter does not work. If you drive off, the rev counter will start to flick up and down and eventually start working again - sometimes after a mile or so, sometimes longer. I'm not sure, but I feel, at night, when the rev counter is not working the lights appear a little dimmer.

Local auto electrical guy has checked wiring out, changed a few dodgy connections on the back of the alternator, but it hasn't helped.

Now.... tonight I'm sure the following happened, although it was out of the corner of my eye, so I could be wrong:

After filling up with fuel, having travel 15 miles or so, as usual the symtoms occured. I drove about 6 miles home and the rev couter flicked up a couple of times, but stopped again. I stopped at the house gate and at tickover, the rev couter started to flick, so I opened the throttle slowly and it started to work properly. As it did so, I'm sure I saw the charge light flash on and off again and the headlights get brighter.

Sounds like an alternator fault to me, but what do you think?

Sorry it's a bit long and involved, but intermittent faults are rarely simple, are they? Thanks for listening!

Alan D.
 
Hi there, I've had a similar problem, in that on some days 1st thing in the morning, I would start the car up (it would sometines seem a bit sluggish) and the battery light would stay on and the rev counter needle wouldn't move. I have a '95 300tdi auto, with 108k on the clock.

After about 20 minutes, say, when pulling up at some lights, the rev counter would suddenly start working and the battery light would flick off. It appeared to me that the windscreen wipers would also 'perk up'.

Now, I had this problem on a long trip across to Czech Republic over Xmas, and even had to be jump started by the AA at the Clackett Lane Services (the battery light flicked out when he started the car; typical!).

I got by through turning the car off and on 1st thing in the morning, until the battery light flicked out.

There is a wire on the back of the alternator that is held in a little black plastic plug, and I thought that was the culprit, so cleaned the spade connectors up, tightened the female portion and added a bit of electrolube. It didn't fix it.

So, when I got back to the UK a few days ago, I got the car booked into my local independent LR specialist and had the alternator replaced. I have to say that I am sure the headlights are brighter and the electrics have a bit more 'zing' in them, and that's no joke!

Are you sure you have had the correct alternator fitted? They come in different ampage output, so maybe you have a low ampage for your car. If I were you, I would (a) check the connector and do what I did, then (b) check the paperwork to see what alternator was fitted, and (c) check the earth connections.

Maybe the recon alternator has dodgy voltage regulator (bushes?). If it is linked to you putting your foot on the pedal, that might be the cause. I think you might want to get another alternator fitted, but could be wrong, as electrics aren't really my forte.

Let us know what you do. And, search around for a good indepenent LR specialist. They are worth their weight in gold, as they will know where all the dodgy earth points are, and what they connect to, etc. Great for spurious fault-finding!
 
Cheers, Tony - sounds like good advice to me. The auto electrician checked all connections to the alternator, so I think I'll go back to the garage that fitted the replacement alternator and find out a bit more about it.

Thanks again!

Alan D.
 
Are you sure that when the rev counter stops working, the battery light stays off? The typical thing that happens is that when the rev counter stops, the battery light comes on.

I still reckon its your alternator, but that point has me puzzled. :confused:
 
The 300 TDi has two types of alternator, the main difference is the size of the pulley.
YLE10124 - To Vin No MA163103
YLE101880 - From TA501920 To VA558898
From TA163104
Both are A127i-100 Amp.

IIRC YLE10124 has the larger pulley on it and uses a larger (longer) drive belt as well.

The rev counter is prone to flicking and dropping to zero on these without there being anything wrong with the alternator (although this doesn't sound the case with yours). It's caused by the spade connector on the rear of the alternator with the White/Black wire. The standard connector tends to loosen off and normally the only way round it is to replace the spade connector.
I had this on mine when I first got it and not had any problems since replacing the connector. ;)
 
Yep, certainly battery light certainly stays off, Tony! Thanks Budgie - that connector has already been changed - it was loose as well! I'll check that the correct type of alternator has been fitted.

Cheers, guys - top advice!

Alan D.
 
Hi
I know this sounds stupid,but with a lot washing and water the earth cable between the chassis and the gearbox gets carroded and makes a bad connection and that can cause a earth problem to some components

I had this on my Defender 300Tdi

Hope you come right

Cheers
 
alan drover said:
Guys,

Do the rev counter and warning light use the same feed from the alternator? If so are they on separate wires?

Alan D
Click to expand...


hi there,
NO - they are two different wires but run next to each other in the wiring loom, which terminate to two different terminals on the back of the alternator. There is the thick Brown wire which we call the +ve (main feed wire positive), the 'no charge light' which controls the function of the 'battery' symbol in your dash board binacle, and then the other wire to control the 'rev counter'
hope this helps
 
Several people have mentioned earthing to me, but I have a gut feeling about this that says if the rev counter and warning light are fed from two separate wires on two separate terminals, the logical place to look for a seemingly simultaneous fault in them both must be the source, i.e. the alternator....right?!

Alan D
 
Thans again, Tony! Will keep you in touch! Won't be this week though as I've just managed to fracture a rib and will be keeping a low profile for a while! Ouch!

Alan D
 
Hey guys, it's fixed! Turned out to be the diode pack on the alternator, so have got the alternator replaced under warranty. Having seen how bright the headlights are now and heard how freely the starter turns on a cold morning, I don't think the alternator has been charging proerly since it was fitted. Anyway, happy ending apart from the hard earned cash that went to waste trying to find what the problem was. C'est le vie!

Thanks for all your help!

AlanD
 
Ex-bosses P reg disco did the same sometimes the rev counter, sometimes the speedo. never had any problems starting though
 
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