93 power steering problem...

First time posting here. I have a 93 Sable/(Taurus) that develops heavy steering when it slows below 5 mph. The problem started all of a sudden. I suspect it has something to do with speed sensitive steering or something like that, but don't know how that works or if the car even has anything like that. How do I tell if I have something like that? I have done a search on the forum for power steering and found nothing that states this kind of problem. The closest I have come to is a thread that stated the Transmission Range Sensor was bad...but that created a slightly different problem. Anybody have any ideas? How does the car lower pressure when it comes down in speed? I would think it would raise pressure as it gets slower.

Thanks for any help you can provide.

Check your belts and make sure they are tight, whats the fluid level like in the car? Are there kinks in any of the hoses? Does it make any noises when someone puts it in drive and trys turning the steering wheel?

like naked dancer said check the power steering fluid and lines,I dont believe there is speed sensitive steering on your car, must be the fluid level or the pump is bad if it wines when the steering wheel is turned. worst case is the steering rack is worn and needs to be replaced, also just for good measure check tire pressure and make sure everything is all clear in the front wheel area.
let us know what you find out