Hello, I have a Trane XL1200, manufactured around 1992 according to the manual, but not sure when it was installed (I'm the 3rd owner of the house). We have not had the air conditioning on as we are in Winter. however, my neighbor pointed out to me that the fan was running constantly for about one week. I cut off power to the unit to see if the contact switch would reset. I turned power back on and then after about 30-40 minutes I heard several popping noises (sounded like a motorcycle exhaust) and saw white smoke coming from the condenser. I cut off power to it and have not turned it on. Any idea why the fan would turn on when we have the heater on inside. And what could have caused the popping noises and white smoke.