Question DELL Inspiron N5110 - white screen on boot up but works with external screen!

Nov 11, 2019
DELL Inspiron N5110 - Service Tag CZHQNP1 / Express Service Code 2826750142

The laptop was running hot - so opened it up and cleaned out the fan of dust and removed the old thermal paste and applied new thermal paste. Closed up the laptop and saw a white screen & no boot-up or Windows screens. However, when I connect an external monitor - the external monitor works and shows that the laptop boot up and goes right into Windows!

I followed your suggestions found on the dell forum for this model:

1. When pressed and held the "d" + power key to turn it back on - this initiated the LCD built-in self-test and I saw the screen with solid changing colors and the system would beep - this seems to indicate that the screen is fine - is that right?

2. Also, I turned off the system and pressed and held the "fn" key + power button to turn it back on - I waited for a few minutes - I first saw a white display and then heard six beeps and then a loud beep, after which I saw the screen with solid colors changing - does this indicate that the LCD is fine?

So where is the issue - with the video card or the motherboard and how to diagnose which and fix it please?

Thank you very much for your help,