Car Broke down! :/ after full revs Any help /advice?

[twoqu]

OK, just checking as those fuses might indicate something else. Obvious first step is to replace those fuses. If they blow straight away then that might indicate an electrical problem with the ecu. Replace them one at a time, S27 first as thats the ecu supply which should allow you to access the ecu.
Can't see how the headlights would have anything to do with the engine to be honest!

http://www.s2central.com/motronic_04_fuses_ABY.html

[newsh]

If something is shorting in the alternator charging loom that could cause a spike in voltage.

[Chris5044]

Hey So I have found that something is blowing the fuse I am pointing at in the picture. Initially it was both of those fuses under that orange clip. But its only the one pointed at now everytime I turn iginition to on, (before engine turn over).

On inspection of rear battery under seat I have seen this white cable snipped too.. is this related? or what is that?

I'm guessing I will have to trace the cable now from this main fuse -- the alternator possibly shorting things out isnt an issue as its all sealed (cabling that i looked at). I've now fastened it away. I think the bulb just went on the light issue as a coincidence.

Anyone any ideas on how to fix this? or fault find?? I cant even plug the dianostics in as its not connecting (prob due to this fuse being out) :/ S2 deffo not going to the nurburgring.

thx guys :/

[Vauhtiveikko]

That box is rear locking diff controller and that blue/white wire you want to cut if you want to keep the rear diff locked also in higher speeds. (Its for vehicle speed).

Forget that and first check alternator and starter wires. Also check engine grounding from right bottomside of engine (finger size wires). Then change those fuses and look for codes. Also check as pointed out how spark plugs look and that engine is turning freely.

[Mikes2]

fuse 27 goes to the ecu pin 18. I suspect the problem is on the other side of the circuit (L30) - http://s2-audi.co.uk/workshop/schema..._aby/page7.png

[twoqu]

As Mike has said S27 is fused directly from the battery not ign. It is to provide power when the engine is shut off for the maf burn off and presumably the ecu memory.
I think this might be an issue with the infamous holding relay. Its a bit complicated but before the engine starts the relay provides power to things like the fuel injectors and when when the ecu is happy it takes over via the fuel pump relay.
I'll have to do some more homework but in the meantime disconnect the MAFand the fuel injectors and see if that makes a difference. If you have enough fuses do it one at a time. That might cause codes for those but its probably academic now as to whats happened.

[twoqu]

Seems the ecu would not like anything above 16V. Only the ecu could tell us that happened!
Possibily an issue with the injectors as they would be on fuse 28 and also interconnected via the the holding relay to fuse 27. Perhaps one or more is stuck open.
Not sure of the spec of the car so not sure whether they are stock or not. If you have a multimeter you could check accross the injector terminas and post the result.

[Mikes2]

I'd consider disconnecting the alternator as well. You've got a short somewhere which is tripping the fuse. It's only tripping with ignition on and is ok before you do this ?

[Chris5044]

I'd consider disconnecting the alternator as well. You've got a short somewhere which is tripping the fuse. It's only tripping with ignition on and is ok before you do this ?

Hey yes this is true, only when I turn the key so the lights come on - it immediately trips and burns through the fuse

[Mikes2]

Suggests the battery side is ok. Same red wires go to the alternator

[Chris5044]

Ok so an update, A friend pointed out a similar fault to mine thats here on the forum :

https://www.s2forum.com/forum/technical/engine-and-turbo/2006358-s2-3b-fuse-27-blowing

I'm having similar issues,

So I followed what they have done and I have unplugged the MAF and tested, and then each injector.

It blew each time.

I then managed to extract the ECU,

with the ECU unplugged it DIDN'T blow the fuse. So its either wiring from ECU to fuse box, or under fuse box (to ecu)

Or the ECU itself. (Now I know this is chipped) So I will follow the guides and the posts what others have done on testing the ecu itself and taking it apart (separating it).

I now have a multimeter..... and calling it a day for now.....

[Greenm3]

Hello,

It could be worth checking the bottom of the fuse box. I recently had a power failure and it was actually the blower motor had shorted and melted the fuse in the fuse box which then shorted others. All cleaned up now and a new fuse box with the fan not connected and it’s all good!
When I first read your post I was concerned it was the woodruff key and the engine had spun up. I had this about 7 years ago. Was a painful experience.

Good luck

[Chris5044]

Hello,

It could be worth checking the bottom of the fuse box. I recently had a power failure and it was actually the blower motor had shorted and melted the fuse in the fuse box which then shorted others. All cleaned up now and a new fuse box with the fan not connected and it’s all good!
When I first read your post I was concerned it was the woodruff key and the engine had spun up. I had this about 7 years ago. Was a painful experience.

Good luck

Thank you! will check asap. Thank you everyone for your help and contributions! This forum is awesome!!

[prj]

If ECU is blowing fuse every time it's connected most likely the car has issues with the alternator and was overvolting the ECU.
The ECU IIRC at 18V collapses a diode and forces ground and power together, to prevent further damage to itself.

Measure the resistance on the ECU inputs between:
PIN 18 and PIN 24
PIN 27 and PIN 24

If you read 0 ohm on any of those, then your alternator's voltage regulator is shot, causing an overvoltage and the ECU frying the diode in itself.
The ECU then needs repair - the diode needs to be desoldered and replaced.

If you have resistance between those pins and they are not shorted together, then at least that part of the ECU is intact.

[twoqu]

Dmitri,
Is this diode the one between pin 18 and 19?
Problem now seems to be the fuse blowing with ign on rather than just hoked up to Bat Voltage and blowing.