External heat pump floor iced, fan some times makes noise?

We are in Alabama. A year ago we were told by a technician on a check of our 6 year old heat pump that there is a leak of freon from the internal unit of our coil. But he did not have the electronic sensor, used soap and I could not see any bubbles. So we called another technician in mid Dec, for a check up. He brought an electronic sensor and could not find leaks. Though he said that there was excess freon and therefore he removed some. Now, from about the first week of Jan. the floor of the external unit ices up. The fan does not turn and louder than usual humming noise is coming from that area. Now, the second technician came and said that the fan has gone bad. Did the second guy make the freon low? Whom to trust? What is the real problem?bladeless fan for salefloor fans for saleelectric fans for sale