Serial adapter not working

Hi, I've bought Serial Adapter FT232RL from ebay ( http://www.ebay.com/itm/181438947135?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 ), but when I try to use it as another serial port with Arduino MEGA, it isn't working. So I uploaded sketch to send millis() every second to first serial (TX0, RX0), disconected Arduino from computer, then connect RX and TX to the Serial adapter, connect power, plug it into PC, open Serial monitor, and it works. So i change

Serial.begin(9600);

to

Serial1.begin(9600);

to use TX1 and RX1, disconect adapter, connect USB, upload sketch to arduino using build-in adapter, then I disconected USB, connected adapter to Serial1, but this isn't working. What should I do? Thanks (sorry for my bad english)

I know what you should do: You should upload the complete sketch (or a smaller test sketch) and a photo of the wiring :roll_eyes:

You can keep the usb connected. That uses Serial (or Serial0).
Just add another COM port with the FT232RL and use another serial monitor program on the computer (like RealTerm or QST). It is even possible to start a new Arduino IDE instance with the other COM port and use that serial monitor.
Not only use “Serial1” for the Serial.begin() function, but also with every Serial.println().

Sometimes those usb-to-serial-ttl converters have 3.3V signals, which can be a problem in certain situations.
I bought the same converter a week ago, so I don’t know yet how the voltage levels are.

Peter_n: Not only use "Serial1" for the Serial.begin() function, but also with every Serial.println().

Thanks, this is the misteake. I used Serial1.begin, but in the code, I using Serial.println. I changed it to Sirel1.println and it works, thanks.