When A/C is on I get this rattle sound. When a drive the car it is all good.
Then when I stop at a light and the car idles I get this rattle or like the engine starts to shake, but more of a rattle.
When I turn of the A/C it stops like 1 min later. All is good without the A/C on
My steering pump fan might be also shot, could that effect that?
My car is a 2005 MCS

 

Guessing you MIGHT be hearing a throwout bearing rattle....
Tensioner could be iffy/bad...that might let the belt move around and cause a rattle....
I'd play with it...

 

What does that mean?
Why should it be affected if I put on the A/C on or not?

 

Belt tensioner would be heard cause the tension/load on the belt changes with the compressor on....
I suggested that the throwout bearing might be the sound cause folks sometimes mistake the sound as being connected to other actions....

 

I know the throwout bearing is also that needs to be changed, but would that make the sound come when I put the A/C on and then go away when turned off?