There are three ways to change it.
1) Get a new chip burned with different parameters
2) Use an EEC tuner to change the parameters
3) Use a thermostatic switch tied into the wiring of the engine computer to override the computer turning the fan on sooner.
The #14 wire on the ICRM controls the low speed fan. If it is cut so it is left open, the low speed winding on the fan motor will be energized all the time. You could hook a thermostatic switch into that with a relay to break the connection at a different temp.
The catch though is that there is a high speed winding in the fan motor that should not be energized when the low speed winding is. If they are both powered, the fan motor will see excessive wear.
The #17 wire controls the high speed winding and is simply grounded to activate the high speed fan.