You decrease the coolant temperatures that trigger the fans on and you can do it by 5 degree F increments or just set them to come on at a particular coolant temperature for the LS & HS fan.
My fan settings with the Diablosport are:
All Conditions, LS On @ 191 degrees F
All Conditions, HS On at @ 201 degrees F
You'll have 6 settings to make for 3 different parameters for each of your two fans.
Here is an excerpt from our knowledge base here on Predator settings for the fans:
The OEM thermostat is 203o F for emission reasons. This sounds like a great example of a useful adjustment, wouldn’t you agree? Here is an example for a Perf CAI 91 Oct canned tune adjustment. If you do not have a Cold Air Intake or run higher octane fuel, select the Canned Tune that best fits your fuel and mods.
Plug in the Predator, choose Performance Tunes > Diablo Tunes > (your current tune) > Modify Tune > Modify Parameters > Cooling Fans AC Off. You will now have six entries, (five showing, one you have to scroll down to). The first entry is “High MPH HS Fan On”. Select this and you will be presented with a horizontal bar graph style slider, it is labeled 150 to 230 degrees, adjustable in 1 degree increments. The current value is likely 198.99 (or as high as 219.39!). Seems a little high for the set point of turning on the high-speed fan when you have a 180o F thermostat. Use the Left Arrow button to bring it down 198 degrees, and then press the Enter Key.
You will be returning to the Cooling Fans AC Off menu, and note there is now an Asterisk “*” in front of the one you just altered. This proves your change and alerts you that this menu item has been changed. Repeat this process for all six of the entries, lowering each by 5 degrees. Make sure to scroll down to the last entry in the list, “Low MPH MS Fan On”. This entry is hidden until you scroll down. You might note each temperature setting has some random decimal amount – disregard this it has to do with the hexadecimal nature of the PCM’s stored values.
Press the Escape key once to return to the Modify Parameters Menu. Now press Arrow Down once and choose “Cooling Fans AC On”. There are three selections here, make the same adjustment to lower the fan on for each.
Remember, a good place to start is LS Fan On at 191 degrees F, HS Fan On at 198 degrees F ALL CONDITIONS. You can play with the settings to suit you if you want but below 191 degrees F as an ON setting for all conditions, your fans will run almost all the time. I know folks who have their LS fans set at 198 (all conditions) and HS fan set at 204 (all conditions).
When you are done, press Escape to back up to the Modify Parameters menu. If you are comfortable with the selections here, you can make other changes as well.