I have a trane xe 1200 heat pump that started making a fairly loud pretty rapid popping sound this morning. It sounds a bit like firecrackers going off. It is too loud to be a cover rattle and doesnít really sound like a knock like perhaps from the compressor. There was a bit of ice build up around the bottom so I poured hot water on it to melt it away. When I restarted the unit it was normal for about 1 minute and then started the sound again. I have repeated this now a couple of times and it runs fine, no sound, for maybe 1-2 minutes then it starts again. I have let it run for as long as five minutes but there is no change. Iím afraid to run it any longer. I have taken off one of the side covers and canít really isolate where in the unit the sound is coming from but if I had to guess it seems like the bottom back right side as you face the unit. Below is a link to a short video I made that has the noise on it pretty clearly. Anyone have any ideas?