diff --git a/firmware/controllers/system_fsio.txt b/firmware/controllers/system_fsio.txt
index 1ad5a4e5c1..ae67f9d86d 100644
--- a/firmware/controllers/system_fsio.txt
+++ b/firmware/controllers/system_fsio.txt
@@ -9,6 +9,8 @@
 # Andrey Belomutskiy, (c) 2012-2017
 #
 
+# different way to have the same result would be using "self"
+# (self and (coolant > fan_off_setting)) | (coolant > fan_on_setting) | is_clt_broken
 FAN_CONTROL_LOGIC=(fan and (coolant > fan_off_setting)) | (coolant > fan_on_setting) | is_clt_broken
 
 FUEL_PUMP_LOGIC=(time_since_boot < startup_fuel_pump_duration) | (rpm > 0)