We had a new trane 5 ton two compressor ac/heat pump installed last Sept. 26. About two weeks ago we noticed a really strong, musty smell coming from the vents. It was a hot day, over 90, and my husband had had the unit in the fan on all the time setting. The smell is only there when the compressor is on. It went away after a couple of hours. Yesterday, it was there again, only when the compressor was on and then again it faded after a couple of hours. I called the company who installed it, and the owner, not a repairman came by. He said he could not smell anything. Had my neighbor come over and she smelled it right away. It started today just after lunch time. It was over 90 again. And again it faded away after a couple of hours. Any clue what might be going on? The factory rep is supposed to come on Monday and check it out.