On the Fiat 850 Facebook page owners regularly ask for a wiring diagram for a Fiat 850. And I have one. Because those posts tend to disappear completely after a week or so (and with that the link to the information) I'll post the wiring diagram here (for a 1967 Berlina).

Elektrisch schema Fiat 850 1967
The meaning of these numbers is

850 schema uitleg
Click the image for a view in full screen

For other 850 (models the PDF's can be found here:

Fiat 850 Special (in English)

Fiat 850 Coupé

Fiat 850 Spider