Carrier® - 3-6T Hailin Low Ambient Control Kit Accessory for Small Rooftop Units service and support

Share the exact alarm, fault, or status message shown on the unit controller, thermostat, service app, or building automation system. Photos of the control screen, unit nameplate, and thermostat/BAS screen help the team understand the issue before dispatch.

Confirm the thermostat or building schedule, whether one tenant space or multiple zones are affected, recent filter or maintenance history, and whether the RTU is locked out, noisy, short cycling, or not responding. Do not open rooftop panels or reset electrical equipment if it is unsafe.

Possible causes include airflow restrictions, dirty filters, economizer or damper issues, sensor or control faults, compressor or reversing-valve issues, defrost problems, refrigerant concerns, electrical faults, or building automation scheduling. A technician needs the full symptom and alarm context to diagnose it safely.

Treat the request as urgent when no heat or no cooling affects occupied space, an alarm or lockout is active, there is electrical odor, unusual noise, water intrusion, unsafe rooftop access, or repeated tenant comfort complaints. Include business hours and access notes when scheduling.