Hi, location of the sender unit & relay unit to test both of these, please !

Hi, my mazda,121 1997 is over heating after I drive it for 15-20 minutes. I had the water pump replaced on it early December 2011. Drove it 2.5000klms over christmas, never gave me any trouble ! I have tested the fuses,the thermofan,checked the radiator for leaks/clogged. All is good ! Now I can not locate the sender unit and the relay unit for testing. I have tried to purchase a workshop manual, to no avail ! Thank-you Anna