hey guys

what can cause radiator fan to run constantly, as soon as I start the car, even on cold engine ?
note that I have evo4 and it doesn't have PWM module as later evos, just the fan itself

so, what malfunction can trigger the fans ?

 

Bad coolant temp sensor, or stuck relay.

 

Your fan control unit is bad. When these go the fans stay on constantly

 

which unit ?
I have no unit that controls fans


p.s. tried several different water temp sensors but still the same

 

which unit ?
I have no unit that controls fans


p.s. tried several different water temp sensors but still the same

 

The fan is still controlled by the ECU, or a temperature switch, you have a bad coolant temp sensor or temperature switch, or a stuck relay..

 

Maybe it was bypassed and wired directly by previous owner.
When I had a problem with by DSM fan controller I wired it up directly on the key start and fan will run anytime the key is on run.

 

yes, the fan is controlled by ecu and coolant temp switch, which I've swapped out three different ones to rule out this issue...
nothing was bypassed worked as it should work, during the years I own this car

haven't checked for stuck relay though..

 

The fan controller is a little black box that sits on the fan shroud. I had a lancer have that issue. As soon as you put the key on the fan would turn on. I would smack the box and it would drop in rpms and bounce around. Otherwise, have you checked for maybe a stuck relay?