Monitor backlight goes on and off fre...

You may have a defective CCFL backlight, it may have the following symptom: Screen flashs on red/pink and off. Picture stays on in red and slowly be come normal. Picture flickering with dim display or appear black. Picture flickering on and off. All these symptoms indicate that the LCD backlight lamp (CCFL Lamp) has reached the end of the life and all you need to do is replacing the CCFL lamp.
Connect an external monitor to your laptop and power the monitor up first then the laptop, if you see the normal Windows images then the video card and laptop is OK and the problem is definitely the backlight. Dim image and/or dark display on the laptop's LCD screen indicates a faulty LCD backlight and it could be the inverter that supplies high voltage to the CCFL lamp or it is the CCLF lamp is nearly burnt out or burnt out, most likely this is the case.
The inverter can be replaced easily but the CCLF lamp is more time consuming and requires soldering skills.
Check out
www.lcdparts.net

The issue could be the cables between the lcd display and the mainboard, or the inventer board, or the backlight itself is going out.

The laptop will require repair, it will need to be taken apart to solve this issue.

Normally this is caused by the power inverter for the lcd. It is a small circuit board right below the lcd, that powers the backlight. If you take off the front bezel of the laptop you should be able to see it, it will have a 2 wire power cord coming out the one end, and another plug in on the other end with several wires.

9 times out of 10 the problem is just the inverter going out, check ebay for a replacment but make sure you get an identical model as the one you have, as they are very specific to each laptop. The inverter will have the part number written on it.

Inverter or backlight problem.
1 connect good lamp(s) to inverter board to check lamp problem
If works ok -repair inverter on the board.
Can not do it by yourself ??? Better (chipper) to buy new monitor