The Volvo 1994 wiring book shows two versions of sensor/pressostat wirings for the Reginas. An earlier and a latter version. Unfortunately it didn't state what year does for the earlier or latter. As such I coudn't be more specific to assist. You'll know which version you have when the radiator fan is running.

By shorting the radiator temp sensor, if power comes via the Red (labelled in diagram as R) wire to radiator fan motor then its the early version. For the latter version, power comes via Green (labelled GN) wire to fan motor. The black (labelled SB) wire is ground.

The wiring book also didn't tell any advantages/disadvantages regarding change in wiring. Regarding the radiator motor R is for high speed and GN is for low speed. Only one is powered at a time never both. This is evident from the internal fan relay diagram.

7/14 - radiator temp sensor
7/38 - grey pressostat
7/40 - brown pressostat
2/11 - radiator fan relay located behind headlights
6/29 - radiator fan motor
31/1 & 31/64 - grounding points


May the diagram below helps,


Regards,
Amarin.