Megane 2 cabrio blowing CAL2(400A) alternator and starter fuse

[simaservis1108]

Hello guys,

Got this customer that is on my back.
After some electronics repair on the car that I did(mostly ECU software stuff and fix of DF038 error) the car is constantly blowing 400AMP fuse.
What happened is:
He was driving on the highway and tried to accelerate,went to 3.5k RPM,then suddenly he heard 4 popping-like sounds from engine bay,and there was a smell of the burnt clutch.
After that car is non start,and no electrics.
I come to the field,found that 400A on positive battery terminal fuse is burnt.
I replace it with a new one.Car comes back to life.
Done diag of ECU,UCH,UCP and ABS,it shows no DTC.
Went to crank the car,it cranks for like half a second,and again fuse blown.

This is complete mystery for me,since I don't do electrics but electronics on the car.
Customer claims I am at fault,and I don't know what to think.
If anyone has any suggestions please feel free to say.
Also in wiring diagram,that fuse is only for alternator and starter.

Regards,
Sima

[smokey08]

Common sense would suggest that the starter motor is faulty and drawing too much current.

[simaservis1108]

Yes but why did the car cut-out in the middle of the driving?
If it was middle of the driving common sense says alternator(starter is not working when driving,only starting?),but common sense also says if it cuts out on cranking(current state the car is in) it is starter.
This is what puzzles me.

[alessioblaupunkt]

Might be faulty ignition switch:
probably he start the car and the starter remain engaged.

[Even if it is impossibile to have starter engaged while engine is running]

If you can, disconnect electric plug on starter,
ISOLATE VERY WELL THE DISCONNECTED PLUG,
fit new fuse, pull start the car or tow the car, see if the fuse blows again.

[rideon]

Might be faulty ignition switch:

M8, the thread is called"Megane 2 cabrio blowing .........."
No such thing as ignition switch on that car..

As for the blowing issues...take a closer look at the big thick wires that goes to starter and dynamo....

[simaservis1108]

Engine was welded together.Car has had turbocharger rebuild and was losing oil.
After rebuild,according to my trusted mechanic,there are 2 types of bearings that should be changed in oil pan.
The people that did the rebuild didn't change that,which caused the engine to lose oil pressure and run dry.
Customer recalled that the OIL lamp was briefly on before the failure.
Ending of the story,car towed away from to the people that did the rebuild.
The car first blew the fuse via alternator,because it couldn't move.
Then the next blow was from the starter which couldn't move the engine.

[rideon]

Don't buy the part where the alternator blew the fuse...
Seized engine ,from the cause you mention,ok, fuse blown while customer tried to restart,ok,
But definitely not the dynamo to blame..

[simaservis1108]

What dynamo?

[rideon]

Well,if you spend enough time on DK soone or later will bump into Meathead's post....
try this...
http://www.digital-kaos.co.uk/forums/f152/how-decipher-what-meat-head-wanted-say-problems-understanding-meat-head-433910/
Got stucked with 'dynamo' instead of alternator,or generator...

'dynamo' was used back in the days wen cars were build,nowadays automobile are produced....

[simaservis1108]

Ah no no,dynamo is OK.

[alessioblaupunkt]

Ok ride, Megrane has silly key. Megrane are rare where I live that's why I mention i/s.
This is the land of VAG.

So customer ruined the engine, told nothing to simas but blame simaservis...
If this happen to me I'll tell the customer to not come back in the future.