Re: touch screen won't calibrate on garmin 2720 gps
The touch screen is a 4 wire resistive type made up of several layers. A thin plastic layer, a micro thin metal layer, microdots for insulators, another ultra thin metal layer, and a final plastic layer. All of these layers amount to the thickness of a sheet of paper. This whole stack is bonded to a thin sheet of glass and placed over the actual TFT display.
It's amazing that you can see through all these layers and only lose 20% of the light. What's not so amazing is that those thin metal layers are prone to damage. I've seen several with no apparent damage that didn't work, and several with visible scratches or cuts that worked fine.
I usually start by installing (or reinstalling) v7.2 firmware and then attempt to recalibrate the screen, sometimes that works. Next I would try re-seating the 4 conductor touch screen pigtail in it's ZIF socket nestled between the big white wires on the display assembly. The last resort is to buy a broken 2600 or 2700 series Garmin and salvage the touch screen. You could send it to Garmin for a flat $250, but that makes no sense at all.
If you get another screen (Garmin won't sell you one), Here's how to replace it: Remove the six screw holding the case together. Split the cases and pull the patch antenna out of it's slot. Remove the four silver screws holding the display assembly into the front bezel. Unhook the small ribbon cable that goes to the infrared receiver under the red lens. Pull the display assembly out of the front bezel. It won't come all the way out because of cables. Use a razor to cut the plastic tape holding the touch screen bracket to the TFT display. Unlatch the 4 conductor ribbon from the ZIF connector nestled between the 2 big white wires. Use a penknife to unbend the metal tabs keeping the touch screen from coming loose. I usually just do the two by the IR receiver.
When you reassemble, don't get frustrated with the gaskets, they're tricky but it can be done. Tom
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You need to recalibrate the touchscreen. Try this: Turn off the Nuvi. Place your finger on the upper left-hand corner of the screen and then push down on the power button to turn the unit on. Release the power button when the Garmin logo appears. Continue to press on the upper left-hand corner of the screen until you see the calibration screen.
Go through the entire procedure of pressing each dot as it appears on the screen.
Once completed the Nuvi will display Calibration Complete This will recalibrate your touchscreen to the LCD display.
If this doesn't resolves your problem. then your touchscreen may be defective.
Turn the unit off. Press and hold down the power button and keep holding it. You will see the screen light up and it will say "pre-boot mode". Keep holding down the power key. It will then say "booting". Keep holding the power button down. You'll then come to the calibation screen. Select the dots and you'll be back in business.
Try to calibrate the touch screen. Push and hold the power button on until you see a white dot on the screen. This is the calibration mode. Touch the dot and another dot will apppear, now touch this dot again, keep doing this until the unit reboot.
If you touch the 1st dot and nothing happens then the digitizer on the LCD is dead. If the unit is still under warranty, get a RMA and return it to Garmin.