heating and cooling prob?

[phillipv_2004]

When i just let my car idle or im at stoplight it heats up fine and comes to a good temp but when i start driving its goes all the way back down to cold?...this really never happened intill recently b/c now it is around 0 outside almost everyday...i have another question...i had a light come on yesterday and dont know what is is it is all the was on the left side of the dash and is all the way down...there is a set of three lights and the one that came on is one the right...mabey this light my play in to the prob above...i know these are pretty noobsh questionns but any healp would be appriciated

 

[GalantGst]

if it is at the middle at idle and goes down to c on highway its ur thermostat.

replace that bi***

 

[92Talon251]

I agree it seems like your thermostat, also that light was it a orange color? If so that is your radiator light it basicly mean your coolent reservoir bottle is empty. which also mean your coolent might be low in your cooling system.