Power steering operation erratic

[MR2Al]

Advice needed please, My power steering operation is erratic, sometimes stiff, then normal, or you have to actually turn wheel back to centre rather it going back to centre almost by itself. This fault wasn't progressive, one day fine next time wasn't, car used to be driven daily but since retiring maybe only once week. Fluid level is ok, but looks dirty, opposite locking it did improve operation a bit, but just as bad next time driven.
I have done a search, I will check and lube u/j, but surely that would not be a sudden issue? Fluid has never probably never been changed so is that the issue, read how to change fluid but as fluid is a bit pricey only want to do it if that is the issue.
If the pump is running smoothly can I assume pump is ok?

Al.

[Carolyn]

Sounds like the lower UJ to me.

If the pump is struggling electrically, you can take the motor cover off and blow out the crud.  Works quite a lot of the time.

[MR2Al]

Fixed, u/j sprayed with a copious amount of Aero spec penetrating lubricant, couple hours later went for a drive, steering fine.