Dispatch for a furnace tuneup. All components of the furnace or operating within the manufacturer specs. During the tuneup, the furnace high limit safety switch was being triggered. After a thorough inspection, it was found that the AC coil is covered in bacterial growth. With the amount of growth and dust on the coil, it is not allowing the heat to pass through. This is also creating the heat exchanger to have premature heat stress marks. Thank you for allowing us in your house to provide the perfect home service and for being a member of the perfect family service club from your LBA Service tech Calvin. If I provided a positive or five star experience. I’d appreciate you sharing your thoughts in a review.