Just Joined to say thanks to forum and previous posters on this topic...the posts led me in the right direction and I have working wipers.

If you have failing wipers you MUST first remove the wiper arms. Remove the three crosshead screws and the black plastic cover at the bottom of the windscreen. The cover has hidden (plastic!) clips - slide it 'down' slightly to unhook them, then lift from the bottom and manoeuvre it off.

Unplug the wiring from the wiper motor (Ignition is OFF, Right?) Undo the two bolts and remove the wiper assembly. Take it inside, out of the rain...

The socket is on a plastic cover that unclips and lifts off...careful with those clips! Inside you will find electrical 'brushes and another 2 connectors...look carefully at the plastic post with a brassy strip over it...that is the earth connection and mine was dodgy. While there clean everything, then gently squeeze open connectors closed and the brassy strip open so it will contact the metal wiper motor housing firmly.

Reassemble install (just the motor), and test

IF you've read this and do it you are likely to repair your wipers without needlessly searching for the clicking 'relay (it's not a relay it's a ***** Body Control Computer) or removing your indicator stalks to test them, or learning fiat yoga position 437A (access and test wiper wiring) OR having to realise that the reason you see voltage for a second only at the wiper plug is because the effing computer is sensing a fault and switching off the voltage and the switches and relays are perfect!!!!!!

As I said...the previous posts I found gave me good clues - and I am grateful for them. I hope this one helps a few. If it clicks (said a previous poster) The Switch and the Computer are probably OK.

Thanks
John

I had this problem back in December!!!

We thought all of the worst things .. BCM, indicator stalk unit... We found it odd that direct power made the motor work but putting it in the car wouldnt work. We made our own switch, but eventually the motor burnt out (too much power I presume).

A new motor fixed it.

We did suspect it was the earth but couldn't find the internal earth of the motor (we had it apart and all!)

But, in my case, I got there in the end. Before the motor burnt out, would have been interesting to try your solution and it might have fixed it :O

Hope this helps others. The issue must be more common than I thought!

The actual wiper motors have not really changed since the old days of proper switches and relays. The gearbox has a tracks and brushes inside that allow the motor to always park in the correct position. They wear, making parking erratic or sometimes the wiper can become slow because the internal tracks are not contacting properly.

The gearbox is grease lubricated "for life" sometimes a slow motor is down to the gearbox bushed running dry. A good strip down and clean with new grease will sort it. Assuming of course that it's not riveted for life as well.