1. Cooling and/or heating set point (slide pots) on ZSM have failed.
2. Zone temperature thermistor ZTEMP on ZSM failed.
3. CC1 or CC2 24 VAC control circuit has opened.
4. CPR1 or CPR2 DISABLE circuit (LPC) opened, during 3 minute minimum ON time, on 4 consecutive compressor starts.
5. Open circuit on programmable sensor terminal 12 at LTB.
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most common problem for cool fail is LPC opening due to refrigerant circuit problem or defective LPC. verify circuit through LPC proper open and close pressures. test while system in heat, defrost & cool mode