Just unplug it, and leave HWmonitor running whilst you go about your activities for a day or so, just in case it gets a bit warm, so you can keep an eye on it but if you are not doing anything stressful i doubt it would get close to being too hot.
I'm only running a cpu fan and I game, an exhaust fan doesn't actually make a massive difference to temperatures, at least for me, but my case is a full size aluminium tower, it might well be more difficult with a smaller case that's got more restricted space.