temperature gauge goes up & down

my cavalier's temperature gauge stays between 1/4 and 1/2 when driving around in cold weather wether its in the street or in the highway, but for some odd reason when the car is parked or in drive but fully stopped for a couple of minutes the gauge goes just a little over 1/2 qucikly this did not happen before, i also have never heard my fan go on but it has been tested and works so i was wondering if this could be due to a bad thermostat...

I've experienced this too, but nobody (my old mechanic included) has been able to pinpoint the problem. :banghead:

What usually runs that is a faulty temp sensor. I am sure sure where it sits at on the Cavalier, but I had a chevy Lumina that did that and I replaced the sensor and it seemed to fix it. Also you may want to check the electrical cooling fan relay

Mine when warm hunts between 1/4 gauge and 1/2 gauge.It will come up to nearly 1/2 gauge and then it rapidly drops down to just above 1/4.Then it slowly starts its march back to 1/2 again.I am going to have to hook up the OBD tool to it when its hot to see what the actual temp sensor/computer is claiming the temp to be.I am thinking its a thermostat acting up.Sorta sounds like the thermostat sticks closed and then rapidly opens up,then when temp drops below a certain point it closes again.The temp sensor was replaced,and aside from the OEM one being covered in a slimy substance,there was nothing wrong with it.Car does not overheat and I have yet to see past the 1/2 gauge mark,and have never heard the radiator fan come on.

yea dat sounds like my problem to, i hav had the thermostat gasket replaced once and i dont know if the thermostat went bad and neep to replace it i still need to check that out...

my temp gauge used to work its way up to 1/2 and just sit there but lately i have noticed its moving up a notch every couple months....its slowly workin its way up there...its like 2 or 3 nothces away from 3/4ths....any help is greatly appreciated...