I have a mega and 1602 LCD display with a IC2 serial board
When I try to run a sketch to find the address I get
No I2C devices found
I read a post or two that pull up resistors 10k are needed but that didn't make a difference. I have two of the I2C boards and same thing with both (although i didn't solder the second to an LCD)
GND to GND
5v to Vcc
A4 to SDA
A5 to SCL
Hi
Have You tried starting up using only one LCD? Else, try that.
I use an UNO and I2C LCD, 20*4 so if the library I use will work for You I can't say.
Look at Rbotics:Speedometer usung UNO and GPS. Copy what You like.
The 44780 library picks up the address of my I2C LCD. How it works with 2 LCD I can't tell. I assume You must put in a strap and change the addtess on one display.
Hope it helps.
Trickyrick:
I have a megaA4 to SDA
A5 to SCL
A Mega uses pin 20,21 for I2C.
Leo..
And you're using the proper pull-up resistors?
A Mega uses pin 20,21 for I2C.
That's the main fix you need.
More information about different I2C LCD's here:
http://arduino-info.wikispaces.com/LCD-Blue-I2C
makes a big difference when i have it on the right pins 
Now that I have it up and running I notice that the i2c has a pot on the back to adjust the backlight but there is no adjustment really to me made I have to leave it all the way to the right or Ill get no display
Is that right or do I have a defective i2c or LCD
Thanks
The pot is for contrast, not backlight. It is not unusual for the pot to be at or near the end that brings the contrast pin near ground potential.