37MGRA PH 91 (Low temperature protection of evaporator diagnosis and solution) – Carrier Enterprise Technical Services & Support

Diagnostic codes covered

PH 91

Description: When evaporator coil temperature is lower than 0°C in cooling mode or drying mode, the unit stops. It starts again only when the evaporator coil temperature is more than 5°C. Recommended parts to prepare: Connection wires, Evaporator coil temperature sensor (T2), Indoor main PCB Troubleshooting and repair:

Troubleshooting workflow

PH 91 (Low temperature protection of evaporator diagnosis and solution) workflow — PH91 (Low temperature protection of evaporator diagnosis and solution) workflow

Related diagnostic checks

37MGRA Temperature Sensor Check

Workflow source: original 37MGRA-02SM service-manual PDF. Error-code names cross-checked against 37MGRA-04SI.