HMI touch screen not responding: the startup test that decides

What the symptoms point to

Read the symptom before you power anything down:

• Nothing responds anywhere, and the setup menu will not open. The fault sits in the touch path or in power-up itself; the startup calibration test below tells you which.
• Presses land off-target, or the edges are dead while the center works. Calibration has drifted, and recalibration is the fix.
• One patch is dead, under the button the crew presses most. Resistive film wears where it is pressed; the typical manufacturer rating is about 1 million presses at a single spot.
• Calibration answers but the project screens do not. The sensor is fine, and something in the project is covering or gating input; the project checks at the end of this article apply.

Clean the face before the electronics

Dirt, liquid and pressure all stop a resistive surface from reporting a press, so rule the face out first.

1. Look for anything pressing the glass: a box leaning on the bezel, a taped-over patch, a swollen protective film, a bezel screw binding on the frame. Relieve what you find and retest.
2. Wipe the face with a soft cloth dampened with water and let it dry for 1 minute before power goes back on.
3. Touch three spots with a bare fingertip, lightly: one corner, the center, and an operator button the crew presses every shift. A screwdriver tip can tear the film and settles nothing.

If a spot now answers, the fault was surface or pressure. If nothing answers anywhere, run the startup test.

Run the startup calibration test

Panel off, press a spot on the face and hold it lightly while power comes on. Vendor FAQ documents describe the method the same way: keep the finger on the glass through the whole start-up process, and calibration opens directly when the boot finishes. On many panels the spot is the upper-left corner; the manual for the panel in front of you prints the exact corner, and some models want a light hold anywhere on the face.

The test reads the touch path with the project out of the way, because calibration runs before the project loads. A project that blocks input cannot interfere with the result.

• Calibration opens. The sensor and its controller report presses. The fix is calibration, or a project check if the project screens stay dead.
• Calibration never opens. The touch path reports nothing, and one restart confirms it.

If the runtime itself still runs and you can reach its system menu, try calibration from there as well. One runtime documents the path as System Banner, then Display, then Calibrate Touch, and its help page shows the pattern: a target appears, you hold the center of it until the color changes, then the next target appears.

One controlled restart, then decide

Write the symptom down before you power off: which spots respond, if any, and whether the display itself is live. Power the panel down the way the machine's shutdown procedure requires, keep the power off for 10 seconds, and apply power while holding the corner through the whole boot. Run this once. A second startup that repeats the result is your confirmation; after that, more power cycles and edits to the PLC logic or the project settings change nothing, because a touch path dead at power-up ignores both.

A panel that keeps restarting has a different fault tree; the article on an HMI screen that keeps rebooting covers that symptom.

Scenario: two panels, two decisions

A packaging line runs two machines with the same panel, and both operators report the same thing: no touch, no setup menu.

Panel A: the face is wiped and dried, and three spots (a corner, the center, the cycle-start button) answer nothing. Power off for 10 seconds, restart holding the upper-left corner through the boot. Calibration never opens. One repeat startup confirms it. Decision: dead touch input. The panel goes to the service desk with the model, the symptom and both startup results. Time at the panel: about 15 minutes in all, counting 2 minutes of cleaning and drying, the 10-second power-off and the two startups.

Panel B: the corner hold opens calibration on the first try. Every target is completed, holding the center of each until it changes color, and afterwards the setup menu opens with one press. Decision: calibration offset, fixed at the panel with no parts.

Same symptom, two decisions; the startup test is what separated them.

The fix, result by result

Calibration opened:

• Complete every target and skip none: hold the center of each until it accepts the point, because a skipped point leaves the old offset in.
• Retest the three spots from the face check. An edge that stays off-target after a fresh calibration points at wear or damage, and that patch is service work.
• Open the setup menu, then run the operator screens the shift actually uses.
• If calibration works but the project ignores touches, the fault is in the project. Two project-side cases have their own write-ups: a startup ON button that blocks the setup menu, and taps that land but a hidden setup screen that never opens.

Calibration never opened:

• Stop field work. A touch path dead at power-up, on a cleaned face, after one controlled restart, is service or warranty work. Carry the notes with the panel: the model, the symptom, and what the two startups did.
• While the panel is away, the work cell still needs the line status. A standalone status board can carry it offline, and our shop-floor displays are built for that job.

Recommendation: make the corner-hold startup test the first electronic check on a touch panel that answers nothing. If calibration opens, recalibrate and then audit the project. If a cleaned screen and one controlled restart still cannot open calibration, treat the touch input as failed and send the panel in, because no recalibration attempt, power cycle or project edit brings a dead touch film back.

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