Rep Power: 0

2000 honda civic. I replaced my battery and noticed the radiator fan instantly turned on, strange considering the car was cold so I did some searching and a little troubleshooting. The car isn't overheating, the fan turns off when the key is in the "on" position but turns on when the key is in the "off" position. with the key in the "off" position I pulled both "12" & "13" from this illustration http://www.hondaautomotiveparts.com/...TAT+%28SOHC%29 and the fan stayed on, I noticed the fan relay clicked intermittently so I swapped relays but it continued to click intermittently, that relay is getting an erroneous signal to turn on the fan but idk what controls that circuit. I drove to work, turned off the car and the fan stayed on for a good 30 min so I pulled the relay, a few hours later I put the relay back in and "on" came the fan, (keys in my pocket). I haven't had time to check anything else but please any would be great

 
Rep Power: 519

The temp switch on the thermostat housing and the PCM, both can control that relay but if you check out a wiring diagram the coil of that relay is only powered up when the key is on.

I'd look for the (radiator?) fan relay being stuck on instead. Contact points welded or stuck together. Get it to act up and whack it with a screwdriver handle or swap it with another identical relay.