This tip applies to the Dell Inspiron 5160 but may apply to other models, even makes. Note: This requires a moderate skill level to do.
The video works fine intermittently pixelates or goes blank even using an external monitor.
Spend $200 on a motherboard or check this. Take the keyboard out & remove the lcd screen assembly.This will rule out the lcd & inverter as a problem. The lcd assembly is fairly easy to remove as a complete unit, no need to take the whole thing apart. Then hook up an external keyboard, mouse & monitor. Power the unit up. As soon as there's a picture on the monitor you can now try this test to verify what I've come across. Lightly press on on the metal shield directly on the screw that holds it to the video card assebly. This is a little left of center under where the keyboard was & it is the only screw that is remaining holding the shield in place. If the screen starts to act up, then you have to do this to correct it.
Power the unit down, disconnect the ac adapter, remove the battery & disconnect all the externals you connected previously. Now put the unit on a solid surface with ample light to work in. Remove the metal shield you pressed on by removing the recessed screw holding it down. Slide the shield toward the rear slightly, gently lift the right side of it & slide toward the right side of the unit to remove it. Remove the 2 screws in the center under where the lcd was. Turn the unit over & remove all the screws from the bottom, including the hard drive itself. Note the screw under where the hard drive was & under where the battery was, be sure to remove them also. Flip the unit back over & take the top plastic off, theres a plug for the mouse pad that needs to be disconnected, it just unplugs, no ribbon cables to fuss with. Now this exposes the cpu heat sink & fan. Remove the heatsink & fan assembly. Remove the video card, 2 screws diagnonaly hold it down. Theres a small heatsink by the cpu covering some transitors, remove the 2 screws holding it down, unless it just pops off with the bosses still attached like the one I was working on did. If this happens, then you found what caused the whole problem to begin with!
Here's the fix:
You'll need to separate those screws from the bosses. Just hold the boss still with a needle nose plier while removing them. Ok,here we go. Using a small flat head screw driver,such as a jeweler's, carefully scrape the area where the bosses would be attached to the board,taking care not to scratch the motherboard itself. It doesn't have to be super shiny,just as good as you can get it without getting crazy. Clean the bottom of the bosses using the same method. Now you need epoxy, I reccomend a one to five minute epoxy like Perma Poxy Clear from Permatex. To do this whole repair I removed the entire motherboard, but it's not neccesary,just makes it easier to work on. Mix a small amount of epoxy & dip each boss bottom first (the side with the nub that goes in the board,not the sides or the threaded end). Do one boss at a time. You got to be quick, since the epoxy will set in 60 seconds to 3 minutes,depending on which epoxy you chose. Install a boss onto the board,they are 2 different sizes, so you can't mix them up & hold it firmly in place for about 20 seconds, then do the other,same way. Once both are in, you should still have a little time before the epoxy sets, so press & hold them down firmly for atleast 60 seconds. Ok, the hard parts are over! I'd wait 2 hours before starting re-assembly. Reverse the process to reassemble. When you tighten the screws for the bosses you fixed,take care to just snug them. There's not much holding them solid to the board, although it's surely stronger than factory now. When you put the video card heat sink in tighten those real tight all but the one closest to the cpu, this one is one that was repaired. that one just gets snugged.Re-install the cpu heatsink & fan assembly, make sure to wipe all the old thermal paste off & put new on the cpu, use Artic Silver or equivalent. I usually put a dot (this is about the size of a pencil eraser) dead center of the cpu & 4 additonal smaller dots near each corner. You don't want it oozing out the sides. When you tighten the video card itself back down, you should really crank down abit on the 2 diagnonal ones you removed earlier, don't go nuts though. When you get to the top metal sheild part, the same applies to the recessed screw, tighten it hard. Re-assemble to the point where we were in the beginning for the test, leaving the keyboard & lcd off. Put the battery back in, plug all the externals back in the way it was for the initial test. Power the unit on & perform the same test as in the beginning. The screen should work well, you'll find if you press too hard the screen may act up. This is as good as it gets,hopefully it takes significantly greater force if it does happen. The reason this screen problem was those loose bosses allowing the video card to move ever so slightly & over time has either loosened the connection in the socket or the connection at the motherboard itself. There's no absolute fix other then to replace the motherboard for a current cost of $200, not worth it for an older machine. If you're a pefectionist, like myself, you can try to stablize the video card further by finding a way to hold it from moving/vibrating by fashioning a bracket or something on the end that that the card plugs into. I'm still working on that part at the moment, I just wanted to post this while it was fresh in my mind. I've included some pics of the board & bosses so you can see what to look for. It's very obvious. I hope this helps, I could not give a complete guide to this repair in laymens terms, nor go absolutely screw by screw on this repair due to it would take about 4,000,000 words & whole lot of pics to do so. Like I said in the beginning, this repair is assuming that the person attempting this has a moderate skill level with taking things apart or knows what they are doing. A complete beginner should NOT attempt this repair!
Good luck, not a total gauruntee for a fix, but it worked for me. The extra re-inforcement of the video card is up to your own creative talent, just make sure whatever it is doesn't interfere with the keyboard installation or pushes that metal shield up. Pics are at this photo bucket link due to file size: http://s648.photobucket.com/albums/uu210/mackbolan/Me%20and%20the%20Dell%205160%20saga/