At the end of the day, if the unit is playing up, it should be replaced.I was actually going to make a thread on this at some time. My Lancer's fans will often come on full tilt with just the ignition on for about 10 secs, then go back down for a bit, then back up, or just on and off erratically. They stay on for about 15 secs after I turn it off as well.
They work well when driving though, so maybe best not to fiddle unless need be?