Dim screen on Dell Latitude D800 laptop

I have a Dell Latitude D800. I’ve had it about 3 years and about 2 months ago, I opened up the screen to a dim (faint) image. After a review of common problems, I know that my backlight is failing to come on. Typically I can close the lid and re-open it after a few seconds and I can receive 5 – 20 seconds of lit screen before it goes dim. Depending on how long it takes Windows to login, I can usually do a Send/Receive and sometimes even read/reply to an email or two.

I took off the LCD frame and reseated the video cable to the LCD, as well as the plug going into the FL inverter from the laptop. That didn’t fix the problem but it didn’t get worse.
Also, I’ve connected an external monitor successfully. The display on the other monitor has 0 issues.

Most likely your problem is related to the screen inverter. The screen inverter works as a power supply for the LCD screen backlight. When inverter fails, the screen backlight stops working at all or it works for a short time, as in your case. You have a good chance to fix the problem if you replace the inverter board witch is not very expensive and is easy to access. You can find a new inverter board here and replace it using these instructions.

If replacing the inverter doesn’t help, apparently there is a problem with the backlight lamp (CCFL bulb) inside the LCD screen.

Also, on rare occasions, the backlight failure could be related to the motherboard failure or the video cable failure, but it’s not very common.