An air system malfunction in a refrigerated air dryer can occur for several reasons. Here are some possible causes and solutions:

Clogged filter: A clogged filter can restrict airflow, causing the air dryer to malfunction. The solution is to replace the filter.

Faulty thermostat: The thermostat controls the temperature of the refrigerant. If it is faulty, it can cause the refrigerant to either overcool or undercool, leading to a malfunction. The solution is to replace the thermostat.

Refrigerant leak: A refrigerant leak can cause the air dryer to stop working properly. The solution is to locate and repair the leak and then recharge the refrigerant.

Dirty condenser coils: Dirty condenser coils can reduce the efficiency of the refrigeration process, causing the air dryer to malfunction. The solution is to clean the coils.

Electrical problems: Electrical problems such as a blown fuse or tripped circuit breaker can cause the air dryer to stop working. The solution is to replace the blown fuse or reset the circuit breaker.

In general, regular maintenance of the air dryer can help prevent malfunctions. This includes cleaning or replacing filters, checking for refrigerant leaks, and inspecting electrical components.