I've noticed that mine comes on as soon as the ignition is in accessory, whether it's been running or sitting for days; I believe it should not come on until needed? And today while messing with the Sube, for awhile it suddenly wouldn't come on with the ignition on, then went back to doing so (hadn't been driven since yesterday, and temps were a mild 63F outside).

Does the car have AC?

 

The aux fan should kick on when the climate control is set to Defrost or when using the AC

sounds like it is in D check mode, ie, the connectors that are for checking CEL are connected. These are under the sterring column. Green and black single wire connectors.

 

They are not supposed to be connected unless checking the CEL. When they are connected, they will cycle fans on and off no matter what..when switch is to on or accessory, car does not need be running.

 

that is for 91-94 legacy, and I am pretty sure other models as well including loyale and impreza.

I'll check those plugs tomorrow, thanks.

(damn, it was a pain getting those panels back in place too, too much extra crap shoved up there).

What kind of car is this for? If it's old gen it sounds like a fan switch grounding. The wire connected to the fan switch could have even become disconnected, broken, or insulation worn down and the wire is touching metal, thereby completing the circuit intermittently. The switch I am talking about is the one connected to radiator (passenger side tank).