Fan Relay Override

I have a 95 T'bird. It has a computer controlled 2 speed fan. There are 2 wires in a large harness that controls the fan settings. For low speed fan wire 14 has 12+ volts and the voltage is removed and the fan comes on (cutting wire 14 will result in low fan always being on with the key on). For Highspeed fan wire 17 is sent to ground and wire 14 continues to have 12+ volts. They are never both on at the same time. I need to figure out how to wire a 3 postion switch 1) on 2) off 3) on. I need pos. 1 to turn on the low speed fan, Pos. 2 to be the off position, and, Pos. 3 to be the high speed fan on. But, I want the computer to still be able to work on its own. The problem is way to high a factory setting on temp to operate the fans in my climate. But I also need to make sure that If I have the low fan on with the switch and the computer wants to turn on high fan that it can turn off my relay if I am in the low setting on the switch. Or if the computer wants low and I want to turn on high with the swicth I can overide the computer. But most important all the combinations cant have high and low going on at the same time it wears out the fan motor. I need this all to run from a switched power source so I dont run down a battery by thinking oh it will turn itself off (like my other car does after a 2 or 3 minute power off cooldown). I have a factory manual with schematics. I can email scanned copies or post if need be.

Thanks for offering to help. I have been snowed in at work. I am off friday and will test those connections and post the anwsers for you.