I have the same problem too...My radiator fan does not come on either on my 92 Civic - I have tried everything...I bought an OEM (made in Italy) temp switch and thought it didnt work because of that...I broke down and went to the Honda dealership and spent $32 on the part but the fan still does not come on - BTW - I also changed out the relay...another $30+

I turn the air conditioning on and the radiator fan does not come on either...I know the fan works because there are two wires that plug into the sensor and when i connect them together the fan turns on - hot or cold...

I have heard that it may be due to a blown head gasket which is fooling the temp sensor??

any suggestions - its gonna start gettin' hot out here in PHX!