For everyone that looks to make quick splices in wires just to get things working; I say this. Always take the time to make perfect solder joints with heat shrink tubing which can be slipped over the connection after. Save your self a lot of trouble from trying to find shorts later on just to figure out that the butt connector was not seated or crimped properly. Just solder it and use shrink tubing to cover the joint. Our cars demand a lot of preventive maint. Save your selves some headaches.
Now saying all that... I am an aircraft mechanic and we never use any mechanical but connectors or quick splices. Lives depend on it. So why trust you beloved fiat and your life to the same BS connectors. Do it right the first time. Drive her again another day.