The last time I fitted one was the early 80s so 'from memory', turning the knob clockwise (as you look down on the Kenlowe control unit) increases the temp at which they cut in. The instructions stated run the engine till normal temp is reached leave the engine runing to increase the temp buy 7deg F. and set the fan to switch on so set between normal and danger
What i didn't like was the engine has to reach a hotter temp than normal to switch on the fan, so never bothered again with them, I stick to standard fitment.
1997 Discovery ES V8 auto.
Previously for 10 years: 1987 Range Rover Vogue Efi auto.
Previously for 2 years 1985 TVR 350i manual.
STAY FROSTY & USE LOGIC ON DIFFICULT JOBS - Get someone else to do it.