False? Overheating Indicator Warning
 

This concerns a 1997 Neon with 82K miles. Over the past six weeks intermittently the overheated engine warning has come on. The temp. gauge is at the top. This lasts a few seconds and then returns to normal. The engine seems not to be overheated and there is ample fluid in the radiator. My auto mechanic ran the engine for 1.25 hrs with no overheating. He thought the whole instrument panel could be involved. A year ago when the speedometer and odometer stopped working the speedo was replaced and the contacts were resoldered. For this overheating indicator he replaced the temperature sensor but the situation recurred the same day this was done. The mechanic believes the heads are not at issue because other symptoms would appear. He still believes the instrument panel is causing this. Are there ideas on the source of this problem and what to do?