Recently(one month ago)had a retro-fit done on my home. XL 19 I was installed with variable speed air handler and a 5" Air Bear media filter. System works fantastic, thermostat is set on 78 degrees actually gets cold if not wearing a shirt. Problem: On the outside condensing unit as of a week ago there has started a fairly loud popping sound( similar to a small firecracker)when the unit shuts off and when it comes on. Also the condensing unit has started a whining noise,when first installed i had to stand next to it to see if it was running.