coolant fan not coming on--need help bad

I can't figure out why the fan does not come on unless I unplug the sensor behind the dis module. i suppose this is the coolant sensor. how do i correct this problem?

Had the same problem with my 90 xr7, replaced both the sensor and the ircm and had no luck. Ended up just installing a thermostatic switch, bought it at pep boys for about $30. Worked fine after that.