Air conditioning at Yeep Grand Cherokee 97

Hello, good morning, I have a problem with the engine of the Defroster, I think that the engine is yet the air asia the windshield and the inside of the car.
When turning the period in the Power position, only the click of the relay is heard, the engine does not turn on, it goes to its connector, but it measures me positive in the two terminals, I remove in connector and LP I put directly from the battery and turn on.
I think it is missing land, because I apply land of the chassis and turn on but do not control the speeds or the power of the panel, if someone can guide me in this fault, I will thank you very much.