Audi A3/Electrical Fault

If as seems likely the fault is due to intermittent loss of supply, any stored code will only say something generic like 'Battery voltage low'. Unless Audi are really clever, it won't pinpoint the fault for you.

Chris.

If you disconnect the battery then re-connect, does the central locking etc operate? It does sound like a momentary loss of power causing things to re-set. Certainly, things like the ignition switch have been known to do this. Dunno how easy the wiring is to get at? Add a link to bypass the switch and see if the fault stops?

I've got a 2008 Audi A3 2.0T petrol that's got an intermittent electrical fault - radio goes on/off, window auto-up/down resets, clock resets, and central locking opens and closes. Everything else seems fine, and tends to misbehave in the first mile or two, then settles down. Did 250 miles without a peep yesterday. Today, on a 2 mile run, the whole lot went full cycle.

I gather this could be one of a few things - ignition switch is possible according to the Audi-sport.net forum. I've charged the battery - didn't take much on the charger and it seems OK. Any other ideas?

I've been looking at a code reader in the hope of identifying the fault properly, and it seems the one to get is the Ross-Tech VCDS/software - about £270. I don't mind (well . . .) spending that if it works and has a reasonably shallow learning curve. Any opinions?

Does this model have a 'main' fuse or fuse link in the supply lead from the battery terminal? I have found exactly these symptoms on a BMW with a cracked fuse link. Some days ok (presumably when it welds itself back together, then it cracks again).

JB

I had a similar problem with an Ascona in the '80s. The only logical common denominator was the fusible link and I found it hard to believe it would go intermittent (didn't think about cracked). It turned out to be a loom plug not fully locked together.

I have VCDS, where are you?

VCDS is by far the best scan tool for VAG, but as another poster has said, it may not reveal anything more than "B+ intermittent/short to ground", unless the Convenience ECU is shot. If you're anywhere near me (W Mids) i may be able to scan it for you.

Not from memory.

It does sound like a momentary loss of power causing things

Not that easy - in the sense that by the time I'm in there (remove the steering wheel and a bit of trim) it'd be as well to change the switch

- a £30 part.

Mmm - not that I can see. I'll take another look.

Yes, that's how it feels. But they're each on different fuses, and they seem to happen at different times. The radio will go on/off, and a while later the locking will cycle.

Sheffield.

That's good of you (and Mark), but that's a bit far - Sheffield.

VW Passats used to suffer a multitude of similar electrical woes due to the "comfort" ecu getting wet. I believe it's under a seat and blocked drains in the ventilation system can cause these to get flooded. Worth checking.

Tim

I'm in Lincoln... if you fancy making the trip, I'll scan it for you.

That would make me suspect something like a loom plug with different contacts making/breaking at different times. Is there a plug to the fusebox or something similar? If it was ignition they would all go at the same time more or less (they may take different times for electronics to reset/initialize).

There was an audi problem with the windscreen leaking water onto an ecu.

About 20 ecus scattered about, apparently. I'll check for leaks, thanks.

That's good of you, thanks, but a bit far at the moment.

It was the ignition switch - changed it over this morning. Some detail and instructions here:

Bought one anyway - but a fair bit cheaper because it can only be used on 6 cars. Very easy to hook up and interpret the results. MAF sensor is playing up, it tells me.