when should the radiator cooling fan kick in.
Clarification: what issue are you having? Also, what is the mileage, engine, and transmission?
When the temperature sensor tells the computer to turn it on. There is no "when" It's based on temperature.
https://www.autozone.com/engine-management/coolant-temperature-sensor/honda/fit/2008
i cant find ect 1 sensor. I removed the air box and couldnt find it is it under the throttle body?
You may want to see if the fans work by turning on the A/C. If they both run then the fans, their wiring, fuses, and relays are good.
ECT1 doesn't control the fans. It's for the computer. You can see if it's working by plugging in a cheap scanner and observing the ect temp as the engine warms up and reaches operating temp. (you can change the display to show ºF instead of ºC in the settings menu)
Here you'll be able to confirm that your engine isn't overheating.
If you still want to hunt down ECT1 it's on the back of the engine, driver's side, between the hoses.
But like I said, if the fans turn on when you turn on the A/C and the ect temp looks too high on the scanner when the A/C isn't on, then you may want to replace ECT2 on the bottom of the radiator
it doesnt over heat its that the cooling fan doesnt kick in . both fans work when i turn on the air , so thats not the problem. maybe the ect 2 sensor is ready to fail . maybe both sensors should be replaced . and thank you for your input
https://www.ifixit.com/Answers/View/568980/Location+of+ECT+Sensor+1+on+top+of+motor
ECT sensor 2 is located at the bottom of the radiator.