Yuo can try changing the fluid first. mine worked sloppier( steering wheel felt considerably heavier) when the fluid was bad. Replace the current fluid Mercon V compatible Trand fluid and it should work better.
Yes, our power steering pumps calls for mercon V or compatible spec Transmission fluids, like Mobil 1, for example. if you have used nothing but genetic brand power steering fluid during fluid changes, that can potentially be your problem. My suggesting would be to drain your power steering system completely, refill with mercon V, and see if that fixes the problem. I believe the system only contains about 2 quarts of fluid so it won't be very expensive.
it is kind of like what i had a problem with on my 99 taurus it would work then stop then work then stop and when it does work it gets pressurized and blow fluid out the hole in the cap and i used regular power steering fluid (could it be wrong) i do not know but i changed the pump and it seems to work ok still makes noise (bad) but does not pressurize and blow fluid so what i am saying might be the pump
If your TRS switch on the trannie is going south, it will cause the power steering to get stiff real fast. Sometimes moving the trannie gear selector back and forth will temporarily make the problem go away. Connections get intermittent in the TRS, and the computer will falsely signal the VAPS (variable assist) in the power steering to go to minimal assist like your on the highway going 55.
If the fluid is so bad it is causing the problem then just draining and refilling will not clean it out. The internal parts will be covered in carbonized fluid.
Get a turkey baster and three quarts of cheap ATF, does not need to be Mercon V.
Drain the reservoir with the turkey baster and fill with ATF. Drive a couple days and repeate. Couple more days and repeat. Then using a white paper towel put a drop of the fluid from the reservoir on it and look for dirt. If you stoill see black stuff keep doing the turkey baster and refill routine until it stays clean. You will elongate the change out interval as it gets cleaner.
Then when it is nice and clean and staying that way, draw out the ATF and refill the reservoir with some good stuff of your choice.