Keep running Fan and not running Activity Monitor

I posted a problem some time ago, saying that my fan keeps running the whole night. However, I have to repost it because I discovered things are going way more complicated. I did PRAM and SMC reset with my battery plugged in and that didn't fix the problem. Surprisingly, when I called Apple, the fan worked just like normal and closed after closing the lid. After getting home I finally realized why. Every time I plug in my laptop the fan runs crazily, even if I closed the lid. However after I unplug it, the fan goes back to normal. It just like my Mac is running something on its own when the battery is connected. I just updated to the newest version of Mac, by the way. I tried to open Activity Monitor but it won't open. When I use another account to check the problem, however, everything works, including the activity monitor and the fan, even when I'm connecting to the power. I begin to wonder if this could be a virus or something related to my account instead of my laptop. I remembered installing and uninstalling BootCamp Windows and Parallels several times, but both from official websites. I don't know if that will matter. Also, is there a way to check virus without paying anything? I haven't bought CleanMyMac or MacKeeper and I don't really want to buy them.

And once again, those are the battery information.