temp sensor?

[|WYG|SS]

its not on my car but my dad has a van. when going someplace today the temp for waer was up in the high position and then it sat for like an hour and on the waay home it was in the normal position. when driving before he said that it would do that a lot(fluxuate between high and normal position). he says he thinks i the alternater/voltage regulator. i keep telling him that it has to be the temp sensor. could this be a bad temp. sensor? i know i shouldnt be posting here. just wondering cause dont uasualy most temp sesors act up when thery are bad?

[blitzcivic]

start with the temp sensor that would make more sense