Thread: Alternator failure without warning - can it be anything else?

I often see rectifier diodes and complete bridge rectifiers fail when used near but not exceeding their upper current limit. It seems that even when they are specced within their limits they still fail.
When I replace them I always replace them with something with a much higher rating if physically possible.
It may be that heat is a contributing factor that was not considered when specifying the components.

I'm with you on the heat aspect.

Regards,

Les.

I have now clarified the situation.

The car (TDV6 SE) was in the Kimberly. There was a day trip that had 40 creek crossings in 60 km - hence 80 raisings of the car to offroad height in a day. The following day the car was no-longer changing height - was in the normal height position. It was driven for some hours. Some time later the alternator light was noted to be ON. Late in the afternoon, after parking the car for some hours, the engine would not turn over, but doors still unlocked with the remote control. No other tests were done (eg not clear whether lights still worked). Subsequently the alternator was diagnosed as defective. New alternator was fitted and the car driven back to Melbourne without incident.

The alternator has now been checked and, indeed, shown to not be charging. The alternator was not dismantled, so the exact cause of the failure is not known, but it spins freely, there is no play in the axle, and there is no external evidence of overheating or melting.

One possible scenario is that the large number of height changes resulted in the alternator needing to produce high current for a long time and this resulted in overheating and failure of an electrical component.

An alternative explanation is that the alternator simply failed at ~ 95,000 km. From conversations with various D3 mechanics it seems alternator failure is not a rare event in relatively low km vehicles.

I will keep the alternator in the hope that after market parts kits become available that would enable servicing of it.

The Discovery is now being serviced. If any additional information becomes available I will post this.

Originally Posted by MelbD3

The car (TDV6 SE) was in the Kimberly. There was a day trip that had 40 creek crossings in 60 km - hence 80 raising's of the car to offroad height in a day.

I have noted that for you guys, something like above is for the most part, just another routine day trip so the kids can visit Grandma and Grandpa.

I doubt Land Rover has ever considered testing their machines to the extremes that you routinely drive.

I tend to think that Sandringham Estate which I presume Land Rover considers the norm for their products, is just not typical of your daily reality.

I continue to be surprised with what in Oz is routinely considered just another days outing.

Hi MelbD3, I suspect the failure is down to a poor quality alternator as this is becoming an all to common event with D3s all over the world.

There seems to be an abnormally high failure rate and it makes no difference whether the D3 has been doing the Dakar every week or nothing more than the school run everyday, the alternators are just failing.

In your case, the compressor would only be working for a short period of time each time you did one of your river crossings and someone towing a caravan at night, running a few driving lights and charging a few low batteries would easily be pulling CONSTANT currents more than double the compressor requirements for long periods of time and don't have probles, so load is not the direct factor, although it may a contributing factor.

Hi bbyer, you seem to be in a better position than us as you have access to after market alternators at much lower prices and the reason I know this is from a number of USA D3 owners who have posted up how they fixed their alternators after failures.

So the problem is a bit too common just to be coincidence events.

Originally Posted by drivesafe

Hi bbyer, you seem to be in a better position than us as you have access to after market alternators at much lower prices and the reason I know this is from a number of USA D3 owners who have posted up how they fixed their alternators after failures.

So the problem is a bit too common just to be coincidence events.

I would say that there is a lot of selection on eBay USA, but at least here in Canada, say over the counter at a local auto parts store, you get a blank stare, something about not in the computer, and go see the dealer.

Below are links to some eBay USA sources. Rebuilt units are also available from the various USA based Land Rover parts by mail, speciality houses for anywhere from $US 250.00 to $450.00 each - yes, better than Oz.

This claims to be OEM rebuilt $US 240.00

GENUINE OEM DENSO ALTERNATOR LAND ROVER LR3 RANGE ROVER | eBay

This is probably rebuilt and close to OEM but is I think an English rebuild, ALL MAKES ENGLAND; price about $US 450.00
LAND ROVER ALTERNATOR RR LR3 RR SPORT V8 4.4L 4.2L | eBay

This one is clearly after market; about $US 270.00
BECK ARNLEY 186-1268 Alternator/Generator | eBay

Another rebuilder unit; about $US 280.00
USA INDUSTRIES A3205 Alternator/Generator | eBay

This listing for an MPA rebuilt is interesting in that the price is about $US 202.00 and includes the core price of $US 106.00
MPA 15703 Alternator/Generator | eBay

My feeling is that the Land Rover 150 amp alternator is just a bit undersized for the vehicle. In theory it should be OK, but in practice no. This reminds me of an Oldsmobile my sister had a few years back. The Delco alternator would quit about every two years. Finally our mechanic decided to install the next larger sized alternator that was speced for the higher class models and was rated 50 amps higher. After that, no more alternator failures. It is too bad that there does not seem to be say a 200 amp model of the our alternator available. A larger rated unit would rarely ever have to put out at the increased rate, however in normal operation, it may not be working anywhere near practical limits. Somehow I think fuel efficiency concerns have affected what is speced as OK and the alternator rating relies on the load shedding computers to protect the alternator - and that in practice, it does not sufficiently protect.

Hi again bbyer, and this may be the reason LR have fitted the D4 with a 180 amp alternator

Twenty percent larger alternator, now that I find interesting.

I don't suppose the LR4 alternator is available as an upgrade for a the diesel D3, let alone a gasoline V8 LR3? If not a Land Rover unit, then I suppose something else that Denso or other makes. To date, I have not seen anything with the proper case profile and attachment locations.

Sometimes one cannot properly put a larger alternator in as the wiring or fuse sizes are too small in the chance situation where the larger alternator puts out full rated amps.

I had the possibility of that situation in my Beechcraft low wing, (Lycoming O-320), which has a 40 amp alternator running thru a 50 amp main breaker. I wanted to put a 60 amp alternator on, but ignoring paper work problems, in practice it just would not be safe; hence LED landing lights and the like.

Re the 3, I expect the loading shedding systems would just assume the alternator was not capable of more than 150 amps and hence limit the output of anything larger; hence wiring and fuse size would not be a problem.

A 180 amp or similar alternator just may be the solution to improved life. I have always felt that in automotive, 10% bigger was the difference between standard and heavy duty; hence 20% should yield a real improvement in alternator life, or at least shift the failure mode from the electronics to the bearings.

If so, I would think that you Australians are the ones to solve that. It was you blokes that came up with the metal oil pan mod for the ZF 6HP26X automatic transmission; now is perhaps the time for the alternator.