"Woke up to cold house" blower was running but no heat. Checked unit and had a 13 code flash on LED. Made sure there were no obstructions in/out with airflow. Checked and cleaned flame sensor, replaced rollout switch (at advice of tech) and drained all of condensation at bottom of unit... If I reset the breaker and reset rollout switch, unit will restart and run through heating to temp at thermostat before kicking off and returning to the 33 code which later changes to the 13. I have also replaced the thermostat... any ideas It is Saturday and its cold..