Where is the valve to put freon in for a 2004 Ford Focus?

The 2004 Ford Focus does not use freon as a refrigerant; it uses r134a. The low pressure port for the air conditioning system on a 2004 Ford Focus is located on the passenger side of the engine compartment near the firewall. It is typically capped with a blue or light green plastic cap. You may need to look beneath some rubber covers to find it.