Volts,

I highly recommend that you read the following article: http://www.aaroncake.net/rx-7/efaninstall.htm

Despite my earlier post, I would suggest that you go for the proper method of installing a radiator fan; which is to automatically turn it on and off using an electric thermostat or thermoswitch. Manual switching, as you'll find out in the article, can be too cumbersome for the driver and inefficient.