Without Climate Control

Warm air comes out of the vents, and there is frost on the expansion valve

Probable cause: The expansion valve is stuck closed

Replace the expansion valve Service and Repair

Also check for

HVAC DTCs How to Troubleshoot the Heating and A/C Systems (Without Climate Control)

Also check for

Check the old expansion valve for contamination. If contaminants are found, replace the A/C system component Service and Repair that caused the contamination