From my experience your sounds like a loose connection!
Under you bonnet you will see a box to the right of the battery it black and square with 2 metal clips.
Take the top off this box and you will see a panel of fuses. check they are all secure. then this open out a bit like a book, check the connections to the fuses. The one for the power steering is the fat blue one.
If this doesnt solve it look under the steering colum at the fuses and again make sure that they are secure connections.
You will need a volt meter, check the power supply to the power steering pump/ motor (it lokos like a silver barrel shape).
If power is reaching it ok and all the connections are secure then there is a problem with your pump/ motor.
Because in Fiats these are electrical and not fluid you need someone with minimal electrics knowledge, dont take to fiat garage as they say replace the whole thing (costs about 500 pounds!!) but it can be fixed! This is what was wrong with mine!
If you take this part out and open up you will probably see that one of the connections has come loose, so this is what you need to try:
took off the steering engine. After I took off the plate with the relays on it (you must unsolder the connections to the relays to do a good job), I saw that it had some iron fallings from the magnet right in the position of the relays. I cleaned with abrasive band, I remade a junction on one relay .... I also put some varnish (isolating glue) to isolate the connections. Put it all back on.
It could resolve your problem.
Let me know what happens
Monday, 13 February 2006