sometimes the sender is cr*p and so not responding. Id first of all drive for short time then check heat by looking at engine with bonnet open. Dont touch radiator filler cap. Check several time during shortish journey to ensure over heating is not accuring. If no obvious signs are visible (steam or leaks) you can be sure its the sender. Either fit new one or get your local repaires to do this. When it comes to peugeot and electrical bits there great when working but when not your nackered as there garages say needs computer test so costs and then its a small price for replacement but expensive for test times. Rememeber engines need to be watched. These devises cant be trusted hope you have some luck
Graham, May 2006