I have a nasty probleme with my Fabia in the last 3 weeks. First time when it happens , the car won't start in the morning, battery discharged, 9V. Ok, I have replaced the battery, after 4 days it happends again. Flat battery. The battery is charghing at 14,2 V, but over night it gets flat. No lights on, no amps, nothing on. I have measured the consumption and it's about 0,13 mA after i lock the doors and arm the alarm. What is happening ? What is consuming the battery? This does not happens every day, it's random, I can have a flat battery 2 days in a row, or once a week. Thanks for help!:confused:

Sounds like you have a short circuit that is intermittent - not always active. 130 mA won't flatten a new battery overnight. Are all of the car's electrical systems functioning perfectly? Did you make any changes 3 weeks ago?

Yes, everything works just fine, and no, I did not make any changes. I look for a short circuit too, but being intermittent, it's tricky to find it

Check that the glovebox light goes off when you close the door, same for each door and the interior light including the one in the hatch area if you have one. Maybe a dodgy switch.

I have checked them, glove box, hatch, all lights, all works fine

Also if a light was one you would see the current draw.

How did you measure the current draw?

Right after connecting the battery the consumption is a bit high, but it drops after 5 secs. at 0,06A. If I activate the confort module by locking/unloking doors with the remote, the consumption rises, and stays at 0,13 with doors shut & locked (interior lights off). Once I had a 2A consumption for a short time, but after I get into the house to get some clamps to hold the ampermeter and begin removing the fuses, it dropped to normal

Finally I managed to find out what is consuming the battery. It is the alternator/charger. Whith engine running, it is charging, but with engine off, is discharging about 2,5 A. Not allways, sometimes. I have disconected the first fuse from the battery cover (175A) and the draw stoped. The wire goes directly to the alternator (big thick black wire). Any ideas what can be wrong with the alternator?? a diode or else?

a diode

Sounds plausible

I reckon that the diode pack in the voltage control unit in the alternator has gone open circuit, allowing the battery to discharge back through the alternator.

That was my thought too, I guess I have to change the voltage regulator pack which I suppose includes the diodes. For a fabia 1,4 mpi 8v elegance, AQW engine , the alternator is a 120A bosch? Am I correct?

When this happend to me (not in a Skoda) the no charge indicator light (Filament bulb)in the dash lit dimly. Prob wouldn't in the Skoda as they're all LED's these days.

I wouldn't mess about with the regulator - probably cheaper to get an exchange alternator complete. If the diode pack has gone, the rest of the alternator won't be far behind conking out IMHO.

Alternator ratings differ with engine/country of origin/ etc.etc..

The sticky label on the service doc. (or in the boot of the car) will tell you the alternator output.

it is a bosch 90A part number 037 903 025M

And the vag-com error code: 01054 Power Supply Relay (Terminal 30) - J317 short to B+. Does anyone knows where is the J317 relay?

Finally changed the voltage regulator Bosch P/N F00M145225 (for 90A alternator) with another one (upgrade replacement, original bosch) with suits up to 140A, costs around 30 quid (equivalent in UK currency), replacement work D.I.Myself. I hope this sort it out.