Carrier UH

What does Carrier UH mean?

The control has detected an outdoor fan motor failure. Carrier's repair method is to check the outdoor motor, since the outdoor fan is essential for moving air across the condenser. With the fan not running correctly, heat cannot be rejected properly and the system flags UH.

Symptoms

• UH shown on the indoor unit display
• Outdoor fan not running or running abnormally
• Reduced heat rejection from the outdoor unit
• Fault isolated to the outdoor motor

Common causes

• Faulty outdoor fan motor
• Outdoor motor wiring problem
• Obstructed or seized outdoor fan
• Motor failure preventing normal rotation

Diagnostic steps

1. 01

   Confirm the UH code

   Verify UH on the indoor unit display first.

2. 02

   Check the outdoor motor

   Per the manual, check the outdoor fan motor for failure or abnormal operation.

3. 03

   Inspect for obstruction and wiring

   Confirm the fan is not seized or blocked and that the motor wiring is intact.

4. 04

   Repair or replace and verify

   Correct the motor fault and confirm the outdoor fan runs normally and UH clears.

When to call a professional

Testing and replacing the outdoor fan motor involves opening the outdoor unit and working with line-voltage motor wiring near the refrigerant circuit. If the motor is seized or the wiring fault is unclear, have a licensed HVAC technician diagnose and replace it. A professional can confirm whether the motor, wiring, or board is responsible for the UH fault.