After I start my truck I notice that the engine kinda jumps from like 600rpm to like 6500rpm........its like a fluctuation of sorts, and I hear a noise coming from under the hood, sounds like the AC kicking on and off. If anyone can tell me how to fix this and/or why its doing it that would be great.

 

It's probably the A/C compressor kicking on and off..........

 

If the problem is indeed the compressor, and probably is by the description.
Freon expands and contracts very much due to ambient temperature. So in the Wintertime the system pressure will drop.
Also in the Winter, the compressor is turned on with the defrosters to remove moisture from the air, and it has a low pressure switch. So when the pressure drops the compressor will cycle on and off.
If you add freon, I would only put enough in it to stop it from cycling so frequently, because when there temperature warms up, the pressure in the system will increase exponentially, and then it would be overfilled. I would just put two or three onces of freon in and check it again to see if that is enough to stop the low pressure cycle. If it still cycles frequently add a little more, you just don't want to over fill it.

 

ok so I experimented with this and I now know that when defrost is on the noise occurs....can i fix this problem or is it just somehting i have to deal with?

 

Agreed with Tumba, I would try that, should go away. Having the defrost on also cycles the AC.

 

thank you thats what i will do will let u know results