Carrier UH Error Code
Outdoor fan motor failure
Source: hvac/carrier/00f68496__38gvq012-301__crr-38-40gvc-q-2si-english-im.pdf
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
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Diagnostic steps
Confirm the UH code
Verify UH on the indoor unit display first.
Check the outdoor motor
Per the manual, check the outdoor fan motor for failure or abnormal operation.
Inspect for obstruction and wiring
Confirm the fan is not seized or blocked and that the motor wiring is intact.
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.
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Other Carrier Error Codes
System high-pressure protection
Anti-freeze protection
Discharge temperature sensor malfunction (out of range)
Low-voltage protection
Communication malfunction
System overload protection
Indoor PCB malfunction
Low charge
Return air temperature sensor malfunction
Indoor pipe temperature sensor malfunction
Outdoor ambient temperature sensor malfunction
Condenser temperature sensor malfunction (open or shorted)