I have a Bryant (Carrier) programmable thermidstat that has worked without problem for 2+ years. The problem is that the LCD and backlight goes out intermittently during the time the system is not running. I have yet to determine the exact sequence of when this happens but without intervention the normal display will return during the time the handler/compressor is on. This make it impossible to adjust/reprogram or turn off the system when the display is blank. Thanks in advance,

Ben

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Originally Posted by benf

I have a Bryant (Carrier) programmable thermidstat that has worked without problem for 2+ years. The problem is that the LCD display and backlight goes out intermittently during the time the system is not running. I have yet to determine the exact sequence of when this happens but without intervention the normal display will return during the time the handler/compressor is on. This make it impossible to adjust/reprogram or turn off the system when the display is blank. Thanks in advance,

Ben

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Labman knows more about these but I might consider looking for a battery in the unit. These LCD types often contain a backup battery to preserve the program content when A.C. power is lost.

Intermittent problems are usually due to a lose connection somewhere, the wiring, or internally. Check the connections, both at the thermostat and the furnace, R, RC and a jumper if there is one, B or C, and perhaps W.

From there, it depends how brave and creative you are taking apart things not meant to be taken apart and fixed. It is still within reason to examine a plug where the terminals connect to the circuit board. Check the solder joints on any transformer and diodes on the board, and the connections from the board to the display.