I have a 2005 A4 avant, 1.8T, which has developed a few faults over a period of time, I can't be sure if they are connected, but I would value any experience anyone else can offer of similar problems.

First, the car managed to lock itself while parked with the engine running (while I got out to open a gate). Don't know if this would have happened again since, I haven't given it the chance.

Second, at about the same time the external temperature sensor started giving some very strange readings (starting most days at -20 to -30 deg C, gradually warming up, don't think it stops when it gets to something sensible). This doesn't seem to have an impact on how the car is running.

Third, most recently when I competely fill the petrol tank the engine temperature gauge varies wildy, and frequently triggers the coolant warning on the dashboard display. Once the fuel tank is less than about 90% full the engine temperature gauge only varies wildly and triggers the coolant warning when I turn left, and below about 80% full the problem does not appear at all. When starting the car from cold, with a full fuel tank, it runs very lumpy, I even stalled it once (a first in the 4 years I have had it).

Thanks for reading all of this, but the garage have already charged me for some repair work which has had no effect and seem intent on the following the "poke and hope" system of maintenance. I would love to know if anyone else has had similar experience before I spend yet more money chasing these faults.