Are you sure you are not confusing this with the aircon fans? There is a constant fan sound on my car, I put it down to the aircon, periodically the noise gets louder, I suspect the compressor is not working continuously or that is the radiator fan kicking in every now and then.

Is that a similar thing to you are experiencing? If so either you have nothing to worry about, or we both have a problem

 

Are you sure you are not confusing this with the aircon fans?

Thanks. I didn't realize that the aircon would be running unless the engine is running. Is the aircon actually completely electrical or is it just the fans that are running?

 

What richierich said.. however, to test it, turn AC off...

 

Yeah, there are 2 fans, one for engine coolant and one for the air-con system.

 

Probably just the fans, but I don't know for sure.