A/C compresor
 

Whenever the a/c compresor is engaging the car is moving forward a bit so I have to stap harder on the brake. This start to hapend inthe last couple of wheeks so I am wondering if the freon is low. How do I check that. I was looking to the dryer and there are no bubles on that little round visor. Also the a/c is very cold and climate control operates excelent.
Cooling system works fine and the aux fans operate properly.

Since the sight glass is clear and the system is cooling well you don't need to check the charge.

If you did, you do it with a set of manifold gauges.

Good luck,

I did check the presure in the system ( actualy a guy from an A/C place) and is perfect.
Then why the compresor is engaging that violent making the car move forward a bit?

If anything, the engine should lose a little power momentarily upon compressor engagement. I think the problem must be something else. I've never seen or heard of what you describe.

Good luck,

There is typically some provision to open the throttle a bit when the compressor comes on so the engine won't die. Perhaps it is out of adjustment.