I'll start by saying that this worked for me and is not necessarily guaranteed to work for you. That said, I would LOVE to hear how it turns out if you do choose to give this a try. This was successful on three of my panels and while that is a small number, I believe I have heard of many others failing in a similar manner. (touches registering further and further to one side until eventually failing to register at all) I've been using one of those panels for the past few days since the repair and it hasn't shown any signs of stopping yet.
Obviously, it starts with disassembling your lcd. Though most lcds are similar enough that pictures of mine would be appropriate, I have none. I had no idea I would be doing a writeup on this and I was in a hurry anyway, so I have only a short and poorly narrated video. Anyway you should be able to find plenty of discussion about taking your lcd apart elsewhere on the forums if you need help with it.
Once you get the lcd/panel assembly free, you need to separate the touch panel from the lcd panel. Mine was taped on with transparent tape at the four corners. In any case, just get it off. You're going to be putting an open flame on the touch panel and you don't want the lcd anywhere near it when you do.
I recommend that you use a multimeter to test the touch panel before proceding. I haven't yet heard of the controller failing, but that doesn't mean that yours can't be bad. Once again, I doubt that there are significant (any) variances between different panels, but nonetheless I still have no resistance values from mine for you to compare yours to. (the 'in a hurry' thing again) Basically what you need to do is grab the 4 wire connector and measure the resistance of various pairs of wires.
For the purpose of verifying a bad touch panel, it should be sufficient to determine whether any two wires show greater than 10k ohms while you have a finger firmly planted in the center of the panel
If I recall correctly, mine varied from 200 ohms to 2k ohms as I moved my finger from top to bottom/left to right, but I'm calling for a 10k ohm limit just to be safe. In reality, you will likely show infinite resistance or infinitely changing resistance while measuring one or more pairs if your panel is dead. Given enough interest (translation: if anyone gives a damn), I may find time to document a better test procedure, but this should suffice for most situations.
Once you've verified a bad touch panel, it's time to repair it. Assuming that your panel has died in the same manner as mine, here's what has happened: The adhesive holding the resistive film to the glass panel has slightly released over time, preventing the two from making sufficient electrical contact. Given the location of my lcd in my dash and the location of my dash with respect to the equator, I'm betting that it's heat which accelerates this condition. In any case, we need to get the film and the glass firmly reacquainted with one another again. The attentive reader will see where I'm going with this, but for those of you who need a bigger spark to get the creativity going, continue reading.
Here's where I post the short video I made. I won't cite my excuse again (yes I will - I was in a hurry at the time) but it has little to no narration so you'll want to read this paragraph along with it for it to make any sense.
What I'm doing is using a lighter to VERY gently heat up the edge of the panel where the glass and the film are glued together. After getting the adhesive just barely warm to the touch, I apply as much pressure to the joint as I feel comfortable with considering that it's made of glass. Ten seconds of pressure should do it - just long enough for it to cool back down.
I would advise that you hook up your touch panel controller to your computer so that you can intermittently test your panel as you work on it. You may have beginners luck, or on the other hand you may spend a whole weekend on it and eventually return and flame me for wasting your time. You don't need to hook up the vga or power connectors - usb alone is sufficient for the touch panel to function.
video -->
http://www.youtube.com/watch?v=noVnvDXWrj8
I strongly recommend that you start off easy with the heat. If it doesn't work, it's no big deal to go back and try again with just a touch more heat. Don't take this as a ticket to go crazy with the flame, but if it makes you feel any better, I did notice that the plastic film survives the touch of a bare flame. It's nothing like the polypropylene or polyethylene plastic bottles which a flame will burn a hole clean through at just the slightest touch. So go easy on it, but don't be afraid to turn up the heat. And after all, it's a dead panel already right? Can it get any worse?
I was able to determine which of the four wires was showing infinite resistance and ended up getting lucky. After the first try with the lighter, it showed significant improvement. I went back for a more thorough job and was most satisfied with the results. It worked as well as when I'd first installed it brand new. The second and third panels were progressively easier as I grew less reluctant to apply heat and pressure to plastic and glass. The last one took only one try in one place and I didn't even see any need to go over it again. The video is of the third one - it was just as simple as it looks.
Well that about does it. I do hope that this works for someone else as well as it worked for me. And PLEASE reply and let me (and others) know one way or the other if you try it.
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I suppose I'll post an update for anyone interested.
Since the day I started this thread (5 months ago), my touch panel never began exhibiting the same symptoms again. Calibration was spot on every day. It did fail recently, but I feel relatively confident in saying that it had more to do with shattered glass and less to do with melting adhesive. I'm actually surprised that it made it through the summer heat. Is anyone else's still holding up after a repair? It makes me wonder if the problem was in the manufacturing process rather than the selection of adhesive. I guess all I can do is shrug.
Also, my apologies for not replying to anything else. It's not that I didn't give a damn; it's just that I don't frequent this board like I used to.
I heated it up (gently) when still attached to the display but this only made the panel to work an hour or so...I guess until the screen got warmed up.
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