Fault codes covered
41-13
This system operates using both a time and temperature requirement. After a predetermined length of time at a possible coil frosting condition (OCT below 35F) defrost will be initiated. OCT is monitored and will complete defrost cycle once it reaches a target value dependent on model and OAT value. Code 41-13 is triggered when defrost is terminated on maximum time and the target coil temperature has not been reached. This may indicate an extreme amount of ice formed on coil or the OCT sensor not being securely attached to butterfly tube. This fault may also trigger if high winds are present and are cooling the coil, not allowing heat to build and melt frost or ice.
Source: ACHPVSR454-02SM troubleshooting pages.