the thermostat could be a stillborn. it happens. but that issue about cold or hot air not blowing....is the blower motor working?

 

Lol
Yup blower mototr is running on all 4 speeds just fine

 

My point exactly, Juanky.
Once, back in the days of point distributors, my best friend and I spent three days trying to figure out why his car wouldn't start after a simple tune-up. The answer?
The brand new condenser was bad out of the box. Replaced it with the old one, started right up.
It happens, and thermostats are one of those things that it can easily happen to.

 

for the blower to move air it must have an air input. check for stuff clogging the intake. make sure the door actuators move freely. about the temperature issue, i would replace the coolant temp sensor. its more expensive but easier. if the thermostat is good or bad, the temperature gauge should be reading something. then, you still have to work with the heating and ventilation system. hold one. when you say the temperature gauge goes up, then down. how far does it goes up? to the normal operation temperature? then, you say i goes down. how far down? when the car warms up, does the cooling fan kicks in? does it takes a long time to reach operating temperature? if it takes a loong time, then i will say the thermostat is bad.

 

Goes up to about the middle about 10-15 mins after it warms up.When I drive or turn the heat on it starts to go down to C

 

for what i understand, it is very cold in NJ. i would replace the thermostat first.