Your power steering control valve is either stuck or out of adjustment. Get the front wheels off the ground. The valve is on top of the steering gear box. Tap it with a small hammer and test by turning the wheels right and left. If this doesn't fix it loosen the 2 bolts just a small amount (just barely break them loose) and tap it with your hammer fore or aft and test again by turning to the right or left. When it turns with equal force both ways you have it correct. Hope this helps.

Roger