New battery, alt, belts, still no charge.HELP!

[jira]

Hi Folks,

Need some help across the pond here in Virginia. I have a '97 Discovery SE7 with 4.0V8i engine. About ten months ago I noticed on a 2 hour trip that the battery was discharging - headlights grew dim, dash lights started popping on, tach quit working, engine began to stumble. Replaced alternator with aftermarket Bosch as well as belts and battery and all was well. Several months later same thing occurred, so alternator was replaced under warranty assuming the replacement was defective. All was well for about a month when it happened again. I've got two good techs on it and they are having a hard time figuring this out as am I. They are not intimately familiar with Rovers, but they know what they are doing.

At one point it looked like the belt was still slipping, so we replaced the belt again.

Then we discovered that the belt didn't appear to be routed correctly, so we re-routed it per the shop manual.

Next we re-checked all alternator connections again.

Now we are trying bypass jumpers for each cable in turn in case there is a break in one.

Two clues that seem important are that the tachometer, after working sporadically, has quit working entirely and the low voltage warning light doesn't come on even though it should.

We are at our wits end. I've had this vehicle since new, but if we can't get this sorted out soon, it will have to go. A real shame because this Discovery was dead reliable until this recurring problem that we have been unable to solve.

Any ideas? Thanks in advance.

John

[Dizzy Dave]

Hi jirs.
i had a problem like this, and after it was off the road for about 6 months, with a non starting engine, it turned out to be something as simple as bad earth points, to much off roading and no cleaning....... worth a try, clean all earth points mainly the one on the drivers inner wing near the exspantion tank...

[Range Rover Blues]

Don't reley on the warning light as it's a function of the alternator.  In truth what happens is the battery creates the field in the alternator when it first starts untill the engine is running and the alternator generates a higher voltage than the battery at which point the lamp is shorted out via a diode, what is know as 'self-exciting'.  The fact that the battery isn't charging added to the lack of the warning lamp suggests an internal fault.

Can I assume you have tried connecting a volt meter to the battery to check for the voltage with the engine running?  If so there are commonly 2 small connections and one big one.  One of the small ones should be the rev counter and the other the warning lamp.

As stated already check the earth, use a jumplead if you have one.

If you think it's the alternator again look for a faulty heatsheild or similar that could account for the premature failure, alternatively use a different source of spares, it's not unknown for faulty batches to be in the marketplace.  Ultimately alternators are not rocket science, if a few basic checks don't give you the right answers, it's bust.

[TUFFTEE]

I will Concurr on whats been said so far!

A bad earth connection can cause all sorts of differant symptoms?

I don't really know much about the 300 series disco?

But on the 200 series there are fusable links on the inner wing between the battery and the bulkhead! It might be worth checking them if they are there?
                                 Good Luck?

[Sooty]

As all ready said earth problems can give some very funny symptoms.
Just remember the alternator is earthed to the engine and the battery is earth to the body.
Try connecting an earth between the battery post and the alternator bracket.
If this cures the problem then you have an earth problem, not advisable to leave it like that but at least it will point you in the right direction.
Just my two penath (sorry two cents).

[Wanderer]

What can happen is that the Handbrake cable can end up as the best route for an earth between the engine and the chassis then battery.

It isn't unheard of the handbrake getting warm.

I jest you not!

[Range Rover Blues]

I had a mate whos car used to melt the clutch cable every couple of months, depending how much damp was in the crimp on the earth cable (we later discovered).

[beast5680]

its not just the warning bulb on the dash failed? i,ve had it on other vehicles that refused to charge where the bulb failing doesnt allow the exciting current a route so it doesnt tell the alternator to charge?

[Range Rover Blues]

That's a possibility isn't it.  The bulb should have a resitor in parallel in case of such an eventuality but you can't always be sure.

[beast5680]

i only suggested it as i,ve spent many a fun hour on freezing farms looking for electric faults :lol:

[Spooky]

I'll agree with the charge lamp diagnosis - this is the most likely cause of the problems ... it may well all boil down to a 50 pence bulb! :roll:

[petergalileo]

I have a similar problem on mine, my ignition light sometimes glows dimly with the engine running you can only see it in the dark or if you shade the dash with your hand.  The tachometer also stops working.

I found wiggling the wires at the back of the alternator corrects the problem.

I think you have a similar probem with a loose wire somewhere it will be on the thick brown wire from the alternator or the engines earth (as in an earlyer post check the earth straps).  I think the Tachometer on the disco detects alternator pulses rather than sparks so both faults point to loose wires.  In addition, Alternators dont like being disconnected from their battery when the engine is running and can cause them to burn out.  

I would check the thick red wire with a continuity tester while wiggling it.  I would run a thick wire from the alternator bracket to a convenient earth point, this will remove any possibility of the engine earth causing the problem.

Peter

[Wanderer]

Aren't some belts directional?

Sounds daft but somewhere in the old grey cells I can remember someone having to turn the belt around.

[jira]

Are the belts directional? Possibly, certain tires are, we'll check that. Interesting the Factory Shop Manual has the belt routing pattern for for a few of the engine offerings, but not mine. I suppose I shouldn't assume, so I'll check that again.

I believe the low current warning lamp works, it just isn't working when you would expect it to. Seems ridiculous to think that it wouldn't work when there isn't enough current to power it, that's exactly when it should work. Otherwise, what is the point?

The concensus from everyone seems that it is that it is an earth problem, or as we Yanks call it "ground". We do not disagree and will pursue that issue thoroughly, just hoping we can solve it without replacing the wiring harness. More $$$ than I wish to contemplate.

Since the new alternator is not a Rover OEM product, but rather a Bosch, I am wondering if there is some small but significant difference that we have missed between the two. Any experience with aftermarket alternators out there, good bad or otherwise?

Handbrake cable, huh? How in the....... ? Okay, we'll check it out.

Keep the suggestions coming. Snow has arrived, spouse misses the seat heaters, and we need this one back on the road.

[muddyweb]

I'll agree with the charge lamp diagnosis - this is the most likely cause of the problems ... it may well all boil down to a 50 pence bulb! :roll:

That's easy to spot..  does it come on when you turn the ignition on ?  If so, then it is OK... if not, then it is duff ;-)

[Wanderer]

You'll know Tim.
Is it the 300 tdi that has a directional belt or do I need to take more water with it :)

[jira]

Charge warning lamp is fine, belt routed correctly, every connection and eatrth checked and re-checked.

Noticed that overnight the battery is discharging and the alternator is warm. That indicates an internal short in the alternator. However, we have been through at least 4 or 5 - I am losing count - alternators including the original. All displaying the same symptoms but sometimes it takes a few months to show up, other times it takes a few hours.

Is it possible something is cooking the alternators causing an internal short? I hate to do it, but this is the last shot before we get rid of this vehicle.

[jira]

BTW, a quick check of another forum suggests this is not an uncommon problem, but no one seems to have found a definitive answer. A lot of those with my symptoms have replaced the alternator several times, but there is no indication of real resolution.

Thanks again,

John

[petergalileo]

After 1993 the alternator output runs through a fuse, so why not remove the fuse overnight and see if that stops the alternator getting warm and the battery discharging ?

If that works, I suppose you could fit some sort of relay system so the alternator is only connected with the ignition on ?

Just an idea.

[jira]

I think the alternators are fine when we install them, but something is causing them to fail, perhaps something to do with the diodes being a slightly different spec in the aftermarket unit. Or maybe something to do with the pahse or quality of the signal. Just not sure.

[jira]

We might have found the problem today.

There is a lead that comes from the back of the alternator and goes to earth as many of you know. The LR shop manual wiring diagram indicates there is an 820 ohm resistor inline with this lead. A phone call to a knowledgeable independent LR shop confirmed this, and were told to look for a bulge in the harness itself about 6 inches from the connector. We had tested the line for continuity previously, and it checked out fine. So today, thinking the resistor may have failed, we decided to check the amount of resistence in the line and recorded more than 4400 ohms. This was way out of spec and particularly odd since a failed resistor usually results in either an open or closed circuit. When we tried to follow the lead to find the resistor itself and check it directly, we didn't find it where we expected. Then we noticed an interesting jumper between two terminals on the back of the alternator. When we measured the resistance between these two terminals we recorded 840 ohms, clearly in the ballpark. So, that means the resistor is in fact built into the back of the alternator, not in the ground line itself as depicted in the wiring diagram. That also means there should not be any resistance in the earth line itself. So it appears we have a bad earth after all, but one that mimicked the resistor allowing enough current to show continuity, but providing too much resistance to allow the alternator to function correctly. I am willing to bet that this has been a progressive problem over the past 11 months, and that the resistance in this lead has increased over time. That is why the incidents have recurred in greater frequency here of late.

We test this hypothesis tomorrow by bypassing the old earth line with a new one. Wish us luck.

As a result of all this, our Discovery has a new name. Say hello to "Sparky".

John