The turn signals, center lock and power windows do not work in cold weather

This is more then likely an electrical issue however, did the technician check them when it was cold and they were not working? Or were they working when they checked the vehicle?

Unfortunately we don't have a manual on this vehicle as it is not offered in the USA but we do have Fiat's that are similar to this. While this issue is not common I would suspect the issue is with the body control module. Any time there is an issue like this that is temperature related, it is normally an issue with the circuit board on a control module.

How often does this act up? If it is pretty consistent when the temp is cold then I would make sure that is the day you have it checked out otherwise I doubt they will find an issue.

Moisture in the connectors is always possible. We use this gel called dielectric grease. Basically is it like a jelly that is able to conduct electricity that will keep out water. However, I would remove the connectors on the BCM and see if there are signs of moisture. This would be stains or green growth in the connectors. If you find this, you need to replace the connectors as the damage is already done.

I am not sure if he meant the BCM by just saying the board but that would make sense. The BCM is what controls this stuff and if the issue went away when he unhooked the connectors and connected them back up, that would be where I would start. So we need to know exactly what he did for it to start working again so we know what he was touching. As that is most likely the issue.