is my lcd display defect?

Hello everyone,

First of all, I am an inexperienced user and quite new to Arduino. I want to get started with displays.

I have an lcd display 2x16 with a i2c bus circuit board combined with the Arduino/Genuino Uno.

The Wiring is simple:
5V to Arduino 5V pin; GND to Arduino GND pin; SCL to Analog 5; SDA to Analog 4.

The Sketch used:
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x3F); //, 4, 5, 6, 0, 1, 2, 3, 7, POSITIVE);
(I haven’t figured out yet if the pin assignments after the device Adress are needed or not. It wont work either way.) & (The Adress definitely is correct, I’ve run an i2c scanner sketch)

void setup() {
lcd.begin(16,2);
//lcd.backlight();
lcd.print(“HI!”);
delay(1000);
//lcd.noBacklight();
}

void loop() {}

The Sketch can be checked and is okay so far (I think).
The “Power” LED on the i2c board is red.
If I run the sketch, no matter with or without the lcd.backlight or the pin assignments, the screen will glow up for an instance and turn black right afterwards, without back lighting on.
However, if I just connect the screen it will light up with the backlighting on and stay in this state.
I did try out different potentiometer settings.

Also I have to mention, that I’ve tried out other sketches found online, with other libraries e.g. Adafruit_LiquidCrystal_master.

Is my lcd screen defect, maybe the i2c, or am I the one who is?
I’d just get myself a new one if needed.

thank you

sincerely, Lukas

There are several different LCD to I2C expander pin mappings. The hd44780 library will auto detect the pin mapping. The library is available through the IDE Library Manager. In the Library Manager select Displays in the Topic dropdown and type "hd44780" in the filter box. Select and install hd44780 by Bill Perry. Use the hd44780I2Cexp class.