Volvo Repair: 93 Volvo 940, regina system, coolant level

Question
Ihave a 93 Volvo940 with a B230F eng w/ a regina system. The radiator fan does not come on and as a result the car overheats. I have taken the 2 wires that go to the radiator fan sensor(on rt side of radiator) and touched them togeter and the fan comes on.... So, I replaced the radiator fan sensor...Still doesnt come on. So, I replace the fan relay the (three plug) one behind the battery. Still does not come on... So, once again I touched the two wires from the radiator sensor together and IT COMES ON!!!!!! Whats going on I cannot figure this out. Also, all wires/connectors SEEM to be good. Please help. Thank you in advance. Sincerely, Phill

Answer
  Phill, one of two things, you got a bad replacement sensor or it's the wrong temp. Or, your coolant level is low or you have an air pocket. Touching the two wires together rules out any electrical malfunction on the back side. Do you have an DVOM so you can test the switch?

Mark