While in there I managed to get the fan motors working. It seems both temperature switches were broken. When shorted, the relays work as supposed, starting the appropriate fan.
The ones I found was from a Fiat 124 (and several other similar vehicles). One of them closes at 87°C and opens at 92°C. The other operates at slightly higher temperatures (88-95°C if memory serves me right).
Fiat-124-127-128-131-132-alfa-lancia-temperature-switch-92-87/
Fiat-124-127-128-131-132-engine-radiator-fan-temperature-switch
the old switches (below) operate at a lower temperature, so if anyone knows of similar switches with lower temperatures, let me know.