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Álvaro Ramírez

29 December 2019 Fixing Honeywell CM927's dead screen

My Honeywell CM927 thermostat's screen had been getting progressively worse over the last year. As of late, the screen was of little use.

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A random search yielded the Honeywell CM927 LCD screen fail - common? thread, with a promising comment by Phil:

"Strip the unit and remove the circuit board (just a few plastic clips, no screws). Remove the LCD assembly from the circuit board (more plastic clips and an eight pin push connection). Removed the LCD unit from the clear plastic housing (more plastic clips). Finally heat up the plastic ribbon where it is stuck to the circuit board (hair dryer will do trick) and then firmly press it onto the circuit board… probably worth doing this several times; in effect you are remating the ribbon to the circuit board by softening the adhesive. Put it all back together and it should be working again."

Phil's instructions were great. There's also a super handy video by El Tucan, also linked by Stevie.

Success \o/

Heating up the plastic ribbon and pressing it onto the circuit board did the trick for me. Took a few tries for all segments to appear, but the screen is looking great again.

Thank you Internet strangers! :)

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