The climate control system allows the user to set fan speeds between levels 1 and 5. In my truck, level 1 no longer works. The problem is that the compressor still runs, but the fan doesn't, so there is no air movement. Though I haven't used fan speed 1 since noticing the problem, I am always concerned that if I do set it to 1 by accident, the air conditioning compressor may fail due to system inbalance, where the refrigerant does not have a proper environment to expand (warm air passing the evaporator). This could lead to the evaporator freezing over, or worse, compressor failure.