I finally realize why sometime my AC/heater works, and why it doesnt. Its seems during start-up, if the AC logo/light on the dash doesnt light up, my AC/heater does not work...When it is turned on, only a little cool air comes out. WHen I say a little, I mean it's is slightly detectable on the back of my hand..
But when the AC logo/ lights up during start-up with the other lights (oil,ABS,brake,etc..etc..), then my AC/heat works perfectly..

My question is : Why does this occur? How can I make sure the AC light (looks like a snow flake) lights up all the time during initial start-up...It seems the light lights up 75% of the time...What should I check?

Thanks