It's been a week since my 2002 Lancer started to make a weird noise when I steer left or right, but just when the A/C is on, and the wheel feels harder to turn also, what do you think about it?

 

belts.
i have the same problem.
replace your AC/power steering belt, or tighten it. what miliage you at?

 

Your Power Steering Fluid may be low.

 

I have just completed my power steering fluid, it was a little low. the car is right now 60450Km, but I think the former owner had changed the belt.

 

Sounds like ur revs drop when ur making an effort reducing hydraulic power...when the a/c is on it demands more engine power further lowering your revs.. Just out of curiousity try reving to 1k and see if the problem is still there...