Ha - more FIAT forum members in NZ - hello!
I used to have a Tipo DGT with non-operative locking on right-rear door. I don't remember the obvious broken piece but certainly the *#@! thing failed to work in the car despite working fine several times on the bench.
The temptation was always to convert the central locking using one of those $40 kits - excellent value for four motors plus those overgrown terminal-block things that you clamp onto the existing lock rods.
Of course my Fiat Uno, Lancia Thema, etc. had the advantage of using the cheap and common type in the first place - ironically better in the long run, though I'm sure at the time that FIAT's choice for the Tipo was much better quality.
Digressing, but of the 'standard-type' central locking, the original Swiss-made units (fitted by FIAT) are awful - the aluminium gear wears out (and not the plastic gear). You'd have thought that, of all people, the Swiss would be able to make gears. It seems that the current cheapie Made In China units are rather more reliable.
-Alex