The air vents in my 57 plate grande punto 1.2 active are temperamental about when they decide to work Or not. I've taken it to the garage and they replaced a part which again failed to work. After taking it back to the garage again it worked again but only for a couple of weeks. Now it's on and off again. What do?

I had the same problem, the source of my problem was the connector under the passengers footwell, through time some of the pins became loose and weren't making contact

What did they replace? The relay? If so you'll have gotten the uprated part from FIAT, as above, the pins on the original wiring loom don't quite make perfect contact with the connectors in the relay, the new loom connector pins are slightly longer.

SO the solution is either to:

a) cheap fix, wiggle the wire with the fans on 4 so you can hear what position it works in. Need to do this a couple of times a week depending on how busy your passenger seat is.

b) Change the connector on the wiring loom, Vauxhall do a replacement repair kit. FIAT don't. Obviously splicing etc will be needed, an auto-electrician would be easist option.

c) Replace the entire loom. According to some FIAT techs (Hi T ) it can take less than an hour to replace the whole shebang. Loom is about £60 iirc, plus labour probably around £120-£200, depending on garage/time/charges.

EDITED TO SAY: I opted for option a), much to the wife's dismay.