Upon arrival, system was off. Test ran operation through jumper wire on control board. Tested gas pressure and temperature rise as the mentioned 4 flash code indicates an airflow issue and/or overheating. Gas pressure on initial startup and at 3.9inwc when the system specifications are 3.2-3.8inwc. Set gas pressure to 3.2inwc. System was still on the higher end of the temperature rise range of 40-70F at 65F. After some further testing, it was found that the bypass humidifier does not have an airflow damper installed, nor the inner bracket with a humidifier pad. This is allowing an excessive amount of hot supply air directly back into the system artificially raising supply temp and continues to cause it to trip on limit switch even when running within temperature rise specs. Used tape to seal off humidifier pipe to block airflow, and bumped blower speed to Med-Hi from Med to get the temperature rise more towards the middle of the temperature rise. With all current settings, system is
