mrawers

I have a 1999 Jeep grand Cherokee and the radiator fan is not working and I just put in a new relay. I already jumped the fan and it works fine. I pulled the harness off of the heat sensor and the fan did not turn on. The fan also does not turn on when I turn on the A/C, but I noticed that when I used a test light grounded to the negative terminal of the battery and touch it to the small hot wire going into the relay at the harness that the fan will immediately turn on. There are 4 wires on fan relay harness and two if them are hot. When I stick the test light into the small hot wire the fan starts up. I am wonder if this is because it is shorting out the small hot wire and if so what does this mean?