burning alternator,landrover disco 300tdi

Got my 97 jap auto D1 (with EDC) running,finally,thanks to all who posted help. Have been running the engine,vehicle parked,for 30-60 mins a time all day to check for leaks etc.Just when I thought all was good...

....smoke pours out of alternator.So I turned it off.

Earlier on I measured 14.4v charge,all good.But just now I switched on the aircon and in a couple of mins I noticed a little fluid/acid on the battery ( I had filled it a little generously so thought nothing of it)........then the revs increased a little for a minute,then down again,....then smoke from the alternator.

I didnt have time to check what it was putting out at that point as I was more concerned with,well,putting it out.

I am no closer to getting any answers on whats going on. It was NOT the alternator that came with the vehicle (which was labelled GM), that was a Magnetti Marelli of the denso design, of the lucas A127 type......if that makes any sense !

The alternator that had been fitted had been liberally flooded with water and antifreeze on two headgasket failures. So, I fitted the 100amp alt. of the same design that I had on the shelf which was very nearly new but for sitting unused for 18 months.Prior to fitting I had flooded it with switch cleaner and air-line blown it clean and left it to dry completely.For a long time.It has been sitting on thatr car for about 3 months,unused, awaiting head repair.

The alt. was fine, running for long periods until I put the aircon and fan on, at tickover.
Then revs went up,down,up then smoke from back of alternator.Ignition then turned off,battery disconnected.

Granted,this was an old battery but it was fully charged and was holding 12.6 volts and was man enough to start the car.

Could a battery fault cause the alt to burn out under load ? Why would and alt. burn out under load ? And what is it that will have burned ? I dont have the unti here with me to inspect or describe.

I have the one that was watered....is it worth stripping it and cleaning and then using ? Should I source a repair pack for it ? What is it that will need to be replaced ? Do I need to replace the battery at the same time,given that it still gives good numbers on the meter ?

I HAD wanted to get this one into MOT test today,but THATS not happening now !

Any advice,opinions,experience gladly received, however basic....you dont got to be an expert....just tell me what you did in similar circumstances.

You "don't got"? What part of a Bronx accent is that? Oh wait you like gangster movies. The only clue I have here is the contact cleaner.
By the way, just like DeWalt, Bosch, Makita etc. Those alternators you mentioned are all built in the same factory!
From your post I'm afraid to sound patronising because you do appear to have the knowledge but...the right drive belt and pulley? Tight enough?

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Sorry I meant switch cleaner, could there have been an internal short? Was this unit tested previously?

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Howie, I wasnt aware that you were the grammar control officer for this forum or I would have contacted you before posting.Yes,I am aware that all those alternators are the same build but others may not be.
   Contrary to your patronising post it is not a case of the "drive belt" not being tight enough...that wouldnt cause an alternator to catch fire.The unit was tested and there was no internal short.

But thank you for taking the time to reply.

Oh,and I lived in NYC for many years and am married into a family from the bronx.

Note I apologised for any patronising but I had to ask the obvious. I had family in the Bronx but I made sure I spoke Estuary..didn't I.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Howie,saying you are afraid to sound patronising and then doing so is like saying "no offence"....and then giving it. The problem lies with the fact that unless you had announced the said non-intent then no one would have noticed it !

It wasnt the technical part I took offence to it was the grammar/accent part.But whatever,you dont mean any offence so I will take none and apologise for my terse reply. Thank you for taking the time to answer.

No,there was no internal short,the unit was cleaned,tested and fitted and all good. Any damp or cleaner would have made itself known much earlier.It was only when the electrical load was increased that the problem occurred - the engine had been running at idle for about 6 hours in hour long sessions as the new-built cylinder head settled in and the previously problematic engine was checked for leaks etc.

The unit,used as a high output generator by many car builders has a standard output of 100a sometimes increased to 120a by additional internals.What I was after was some anecdotal knowledge of similar situations as I am aware of theory,have experience and access to all the workshop data. The battery did not visibly boil or heat up and only shed a little fluid from an overfilled cell which is to be expected when charged at 14.4v for hours. I dont want to go fitting another alternator ( I have spares) only to have the same problem.

The obvious way round this is to fit a brand new alternator,£100 trade, and a brand new battery,£80......I would rather avoid this if I can.

I currently have another marelli 127 63340004 unit in pieces for inspection and may go as far as to get a service pack to replace slip ring ,brushes,rectifier and bearings....even though the unit seems fine,if dirty.It is certainly a cheaper option at around £20 but means more delay.

   The serpentine belt on a 300tdi engine is spring tensioned at all times so that is not an issue. The heart of the matter is the time that the alt. chose to burn......when more electrical load was incurred.

Point taken, I was having a laugh at your choice of words, certainly not grammar or syntax, yes I'm terribly patronising especially of those who start their posts with "Hi All" or "So I". In fact leaning more to a joke. The patronising part was about belts etc. I had to ask, first question on diagnostics. The problem is I'm not as au fait on charging systems as I am with relays, diodes, motors etc.
I'm hoping Oldspark can comment here. PM him or if no reply by Monday, I'll email him.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thanks Howie.....I tend to be a little snappy when under pressure,so i...apologise. Im pretty au fait with vehicle mechanics and become annoyed when things happen that have no logical reason that I can see,especially on my own vehicles !

Oldspark is the one who usually bails me out,with footnotes and references to back it up.....I will do as you say if he doesnt weigh in.

Grrr.....

I was wondering if the aircon relay(s) are blowing the charge-lamp circuit....

If smoke is from the back, is it the regulator?

Diodes would tend to blow fast (not continuously smoke).

But overheating windings would smoke and be fanned out the back.
However, standard alternators should be self-limiting with respect to stator overloads. (And regulators should not melt rotor windings.)
Besides, what load does an air-con add... not much? Clutches were ~5A which is less than headlights. And the fan(s) shouldn't be too big (whether internal circulation, and radiator booster if fitted).


But - the charge lamp circuit....
The charge lamp circuit has 2 modes of operation.
First is with IGN on, a "tickle" current flows through the charge lamp & thru the rotor to ensure it is magnetised.
The engine then starts and the alternator starts generating.
The 2nd mode is when the charge-lamp circuit - aka the "L" terminal on multi-wire systems, or "D+" terminal on single wire systems - becomes a +12V source.    

[ The L circuit can be thought of as a change-over (SPDT) relay.
The normally closed contact (#87a) is ground, hence L (#30) is ground when the alternator is NOT charging - ie, engine off. IGN +12V is supplied to the charge lamp whose other side is connected to the #30 relay terminal and hence grounded and lit.
When the alternator outputs 12V, the "L-circuit relay" energises and flips over to normally open contact (#87) which is connected to +12V.
If the alternator stops charging, the L-relay is de-energised, hence grounding and lighting the charge lamp... ]

Hence +12V or ground must never be directly connected to the L or D+ terminal - they must always be through some resistance that the L-circuit can handle. IOW, the current must be limited by lamp/s or other relay coils, etc. IE - don't supply raw +12V to the grounded L terminal, nor ground to the +12V L-terminal.


Part 2:
The L-circuit is often used for other things.
EG - older cars used it to control electric fuel pump (so that if the engine stalled, the fuel delivery ceased). Same for fuel stop valves, though these generally applied to carburetted vehicles only. (EFI pumps are (usually) controlled by the ECU.)

On newer cars, the L-circuit is often used as a "engine running" signal.
This can be used in air-conditioning circuits.
Air-cons also often have a cranking interlock - ie, the air-con is normally powered by a NC contact which opens if the starter-motor is cranking. (Often the "starter relay" - the crank/start switch actuates a relay which has 2 circuits: one NC that has the air-con (clutch) feed, and one NO that connects to the starter motor solenoid. So cranking hence supplies power to the starter motor solenoid and breaks power to the air-con.)


It is not unknown for these other circuits to be mis-wired. (I was recently across a problem where someone substituted a dual-pole starter relay for an ordinary relay. I don't think they ever understood that the air con is NOT on when that relay is on!)
Mis-wiring can mean that the L-circuit is effectively shorted to ground (eg, via the starter solenoid etc), hence SMOKE.


Alas I leave you not with a solution, merely a nice simple explanation of complexities of OTHER vehicle controls & wiring.
(Yes, I am a bustard!)

But I'll try to investigate further (yes - those alternator models ring a bell...).
Give me a kick if I seem to delay or forget.

Meanwhile, maybe some other checks can be done...
Any other wiring changes? Seized relays?

Maybe start the engine, then disconnect the L circuit, the turn on the air-con. Mind you, that assumes the alternator still charges without the L circuit (most do, but some don't), and that only the L can be disconnected (some still require other wires to be connected - eg, "S" = Sense to the battery to stop the alternator going high-voltage (though many are limited to ~15.5V anyhow), or the I or Ig terminal for Ign +12V for the regulator).

Yes, I agree that I cant see that aircon makes the load that much more,its simply the 2 facts that a) heavier duty,highe amperage alternators are fitted to aircon cars,and b) thata when the trouble started. There was a little chatter as the air con comp clutch came on but that was a few seconds and cured itself.It was 3 or 4 minutes later that I noticed a burning smell,I thought it was oil burning off the manifold since the head had been on and off,then I noticed smoke from the BACK of the alternator,increasing rapidly.All the rest I have already said.

Thanks for getting onto this mate,you are always a suprb source of help.

The alt is a magnetti marelli 63340004 high output unit,used on loads of stuff,basically a version of the lucas A127 classic,but is different in that it has stud connectors and a straight through shaft (rather than a cup end bearing) with the brushes outside the bearing.Lots of people advertise the repair kits for the lucas and SAY they will fit a marelli but when cornered admit that they wont.The repair kits that dont actually exist go about £20 whereas the one that does is £78 +VAT+P&P.....I can buy a new one with a years warrantee for under a hundred delivered !

I am off shortly to take the burner off the landrover and put my spare one on,hoping that there isnt a vehicle or battery fault that caused this. If it turns out that it IS the above, I will have 2 to repair and lots more work. I will update as possible.

shirker

PS is it possible that a old battery could cause this ? One that charges OK and hold that charge...and starts the vehicle ? Is it ? And how ?

NO,no wiring changes at all. The only extra is the caravan tow & split charge system that I have the fuses out of....and anyway they were put in long ago and were always fine.

Put another , identical, marelli 63340004 high output alternator on the vehicle , same battery....no problems. Drove the car around,put lots of electrics on ,though not the aircon,(!) and all seems fine.So far.

The unit that came off : had the plastic back cover off for a quick look and cant see any obvious signs of any burnmarks , the brushes and ring look OK. However,the front bearing is squeaking with just hand spinning so I would think that it would not be happy at speed. Have been quoted £25 +,+,+ for bearings but since most alts. use washing machine bearings I will source one elsewhere.

Thats as far as it goes for now !

Thank goodness for that. But simply put, washing machine motor = alternator!!

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Indeed,both multi pole three phase devices....must look at the mountings sometime ! A washing machine motor with the right controller would seem to be a good replacent for the motor in my bandsaw that runs WAY too fast for metal cutting,which is what I need it for.

I shall update as the recalcitrant machine gives up its secrets