Hot under the collar but not under the hood

I have a 97 Blazer and was wondering what may cause

1. The temp gauge to read low 140 - 150 while cruzin down the road

2. The temp gauge to read around 250 while ideling and in drive

3. The temp gauge to drop to around 180 while ideling and in park

4. And finally, why does it sometimes blow hot air out of the heater when set in the heater position and then other times cool air

Any Ideas?

The heat from the heater comes from the water your temp gauge is supposed to read. If the air feels hotter when the gauge reads high, and cool when the reading is low, the gauge may be correct. I've never heard of a sticky themostat, but I guess it's possible. I'd also check the fan. Hope that helps.

Hi..I have the exact same problem. No one yet has an answer

i had a similar problem, do you have that orange coolant in the radiator?
if so, get rid of it. The orange coolant over time it turns into sludge/rust color. Flush out your whole system, ratiator, hoses, engine, and dont forget the overflow. And fill it up with the regular "GREEN" coolant.