Hello

I have 2000 Grand Am GT (3400) with 125K and during winter months or any time outside temperature goes below 40 it does not warm up especially if i'm driving on highway. It would up to 130 or 140 degrees (below 1st quarter on temperature gauge) and stay there, so I'm pretty much without heat. If I'm stuck in traffic temperature would go back to normal (mid point on temperature gauge, around 200 degrees) and my heating would work normally. This has been happening since last winter so I'm trying not to freeze in my car like i did last year heh. Coolant level is almost at full mark.

Any suggestions what might be causing this?
Thank you

It sounds like the thermostat needs to be changed. It could be stuck in the open position causing the water to circulate freely and not warm properly. When you sit in traffic, the water has a chance to warm since you aren't forcing air through the radiator. Change the stat and see what happens.