For the second time in a fortnight the clock and trip odo of SWMBO's Octy have reset themselves during the night.

First time it coincided (?) with strange brake behaviour (not this time) so we had the car checked at our garage including a VAG.COM diagnosis that showed nothing.

It starts OK, no signs of undercharged battery (which would also show up through VAG.COM I think?).

And no thunderstorms.

We have en electric parking heater installed (heating element in motor block and heating fan inside). This is completely separate from the car's electric system, but could it cause some kind of magnetic field that affect the car when switched on/off? A long shot...

Or maybe a dodgy instrument unit? There are a few other symptoms, i.e. no illumination in temp/petrol gauges (since it's not possible to switch lamps, the whole unit must be changed, we've decided to leave it) and the rev needle illumination flickers - more often off than on.

Googling through various car forums shows that Minis and Beemers seem to be affected and the usual suggestion is dodgy instrument unit. Sounds expensive...:(

Since fault is intermittent it's terribly hard to pin down

is there any chance your battery is losing connection? or your battery is running down? have you had any problems starting the car recently?

No signs of weak battery, and as I mentioned in first post we did a VAG-COM diagnosis after the first time - surely low voltage/undercharge would have shown up there?

And since the radio keeps it pre-set stations it shouldn't be a loose battery connection. The cable shoes feel as if they were glued to the battery when I shake them. Also unlikely that it should manifest itself only when the car is parked, not when it's running/vibrating?

I'd probably suggest changing the battery as any slightly iffy current/voltage is going to send the car electronics on a most unhappy trip.

It might be worth cleaning up the terminals, topping up the water levels with de-ionised water and popping the thing on charge first just to see.

Cheers, cheezemonkhai, could well be the battery since it (hitherto) has occured only when the car have been parked for more than 48 hours (this time over the weekend). The starter runs OK, but if electronics react even after just a slight loss of voltage battery could still be the possible culprit.

Another £60 or so down the drain :P

Think I'll take a few readings with the multimeter first and see if I can detect any tendency of voltage loss.