Adding power steering fluid - 1999 Pontiac Grand Prix

SOURCE: adding power steering fluid

you have electric steering if it doesn't work check the fuses under the hood

SOURCE: Added new power steering fluid to the old now my steering is hard

First question is : Was the fluid added marked as poere steering fluid? If so, it's odd that the steering would suddenly become hard. What I would do is disconnect the return line (the one that has a hose clamp on it, not a pressure fitting)
Drain the system there and refill with fresh fluid. Since the fluid has not been changed, you may want to do this twice after running it for a few minutes between changes. If this does not restore proper operation then the pump or steering rack has an internal problem and will need to be diagnosed by someone with experience.

SOURCE: adding power steering fluid

You do not add any. If the steering system is leaking,you repair the problem. It is a sealed system other than a removable fill cap. It does not use fluid in the sense you ever loose any

SOURCE: location of the brake fluid input

You'll also need to drain and flush both systems as the two fluids are incompatible. Brake fluid (DOT3, etc.) goes into the brake master cylinder (located directly in front of the brake pedal, except inside the engine compartment...on the left hand side). Power steering fluid should go into the power steering pump reservoir mounted directly to the pump or in a remote location somewhere near the pump. Usually the power steering pump is located on the front of the engine near the fan/serp. belts.

SOURCE: my steering has become very hard

Unless the drive belt to the power steering pump is slack, the pump itself is likely worn out. Fluid leaks can be at any part of the power system, but usually it occurs at points that have seals--either the pump shaft, the assist cylinder, or the control unit in the steering system. Spread some newspapers out under all components of the power system when the truck is parked. The leaks will show as red spots on the paper where they are. Replace the offending component. Hope this helps!