Yes, they don’t last long. mine was only 15 years old. Can’t get the quality nowadays.
I noticed the end of the wiper was gradually moving off the bottom of the screen, so I kept nudging it up. I decided I should look at it properly and found the plastic moulding had separated from the splined connector. I pulled the wiper arm away, and that left me with the nut and splined bit on the shaft. Needless to say the nut was rusted to the shaft, and a lot of torque didn’t shift it.
I used a die grinder with a cut off wheel, a Dremel like tool will do, to slit down both sides of the nut. I slotted a bit of card to slip behind the nut to protect the glass and sealing bush from sparks. Overkill probably, but a new rear screen is EXPENSIVE!!!, and the card was incredibly cheap. With the nut cut nearly through, I played about with it, trying to finish the splits with a screw driver blade. Eventually a spanner helped dislodge it, and I could remove the two halves. Put a M8 nut on the shaft, run it down, then back it off a turn. This is to protect the thread, and to locate the puller spindle. Next get my small bearing puller under the splined bit, and tighten it up, CLICK! and the spline separated. Tighten the nut down, and wait for the new wiper arm to arrive.
The nut was a flanged type, but looked to have a smooth plastic washer embedded in the underside. Has anyone seen such a thing? Is there a reason for not using a normal flanged nut with the serrations on? I can think the sealing against water might not be as good I intend to use some Lanoguard grease for assembly, then it wont corrode again. If you do this, use a heat gun to warm up the grease to make it flow into all the cavities. Anti sieze compounds could be used instead, but they won’t coat over the nut and protect it.
I’ve written this lengthy tome, as something as simple as replacing a part, when the bits are corroded, can cause plenty of grief, and if you get too heavy handed the job can escalate to catastrophic.The next thing to do is to look at the front wipers, and remove and refix them, then if anything fails the fixing will be trivial. Any car you have now is worth looking after, as the government is making life more difficult, and much more expensive.