Heating and A/C

There is heavy frost or condensation on the expansion valve, and frost on the suction line

Probable cause: A restriction in the low-pressure side of the system

Recover A/C refrigerant A/C Refrigerant Recovery, then check the suction line and the expansion valve for restrictions. Repair as needed. Recharge the system to specifications A/C System Charging

Also check for

HVAC DTCs How to Troubleshoot the Heating and A/C Systems