[dscott]

Doug, I'm not sure about the computer hookup. What type of signal does the wire send? Ground or hot. You would also need to know what the turnoff temp would be. On at 180, off at ?.

To hookup the fan through a relay you can buy a standard horn relay and follow the connections as described. All universal relays use the same numbering system.

# 87 to Battery + or circuit breaker on firewall.
# 86 to temp sender on engine (fan sender)
# 85 to wire 151 from Classic harness
# 30 to fan +
Ground the other wire to the fan to the chassis.

To use an over ride switch attach wire 157 from the Classic harness to # 86 on the relay. The fan over ride switch on the dash has wire 157 and 161. Remove wire 161 and attach a ground wire to that terminal.

The temp sender is supplying the ground for the relay. When it gets to the stated temp it grounds itself. That's why you run wire 157 to the same terminal on the relay and supply a ground at the switch. When you flip the switch on you supply a ground to the relay which turns the fan on.
Don