GHC ghost tap issue / only one function and stop button work

"Ghost tap" means the GHC repeats a function itself without a touch.

Sometimes, even if you tap the stop button, it'll immediately restart the function until you turn the machine off from the back switch.

What can cause the ghost tap issue is

If there is a device that can cause EMI interference (i.e. LED bulb, refrigerator, microwave), turn it off and check if the symptom repeats.

Turn the machine off from the back switch, wipe the GHC with towel, dry it, and turn the machine back on.

Check if the symptom still occurs.

If the group head has leakage, it can cause shorts on the GHC board.

If 1), 2) don't solve the issue, you can open the group head cover

and check

if the insulators are wet

if there is corrosion or any kind of discoloration on the brass WPI part

Here's how to replace your group head controller (aka also how to open it to check for the above):

If you have any questions whatsoever, feel free to reach out to our tech support team.

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mirjam created 2026/06/27.