Power steering plug faulty

What year and model is your car, and who told you this?

Story for delay in writing it is a 9.3 440 2006 reg LD56LFE the power steering as gone stiff 3 times now last mechanic said it was a caro plug that goes to the side of the fluid reservoir is the pump attached to this I have replaced fluid with fresh fluid bu t not sure if can just be replaced as a unit any help appreciated working ok but have been told it will go again and my daughter won’t be able to steer it thank you for reply

I would try a replacement used pump off ebay.

Thank you for reply you don’t think it is the carroded electrics that goes to the pump then it’s working ok at present