I have a carrier RTU. The heat side is not working. I am getting 7 flashes on the LED which indicates a flame roll out fault. What causes that, and what should I look to replace?
Thanks

Flame roll-out is most commonly associated with a failure of the heat exchanger. When the circulating blower runs, the outside of the heat exchanger becomes pressurized. Any leakage through the heat exchanger tubes can cause the burner flames to stray. Replacing or resetting the roll-out device may restore brief operation, but the problem will likely return in short order. Make sure the inducer centrifugal end switch has not been bypassed - this is a disaster waiting to happen. The unit should have an inspection panel near the H/X compartment.

Thanks for your prompt and complete answer.