The 1990 Mitsubishi does not have an air conditioning recharge line. The vehicle has an air conditioning recharge port. You can recharge your air conditioning system through the low pressure port on the air conditioning compressor.
The 2003 Chevrolet trailblazer air conditioning line can be found on the air conditioning compressor. The line goes from the compressor to the firewall. The line will go through the firewall to the air conditioner core.
The air conditioning recharge valve on the 2003 Ford Explorer 4.6 is located on the low pressure side of the air conditioning system. Located on the line coming from the accumulator to the compressor is the recharge valve.