Just joined, and I think this is the place for this!

Got an Octavia 1.6, 51reg, 57k on the clock. Started to get problems with the engine temp a few weeks ago - temp gauge in car will read cold, suddenly shoot up to normal, then back to cool and then settle at normal.Radiator was cool to the touch after a 20 mile run. Changed the thermostat, problem seemed to go away, but is back again. This time with a vengeance! as we also have the engine management warning light on. The guy who looks after the car (not a main dealer) thinks it is a ecu problem, but is not sure. We have tried another thermostat, but no effect. The car now runs with the rad fan on pretty much all the time, rad stays cool, engine temp says normal. Anyone any ideas what to do next. My local dealer seems unsure how to solve the problem, or where to start in diagnosi.

Any help gratefully received

Have you changed the dual temperature sensor? And have you had the car checked for diagnostic fault codes?