ok here goes. when i first got my car few years ago (2007 GP base) when i had the heat all the way up it would be unbearable when engine was up to temp. i don't have it up that high all the time i keep it mid way. last few days i noticed that when i have the heat cranked it is as hot as it would be on medium. when i first got the car the temp guage would hover just below the halfway mark. i noticed last few days that when in city going slow or stopped it would hover at it regular spot but when accelerating or on highway it would dip down to just above the quarter mark, and the heat, or lack there of, would cool off a bit. would that be a thermostat issue? the heater core? or as i have read on here somewhere could that be the blend door issue? it seems to me a thermostat issue. is there an easy way to diagnose what it could be?
