P00144
Carrier Transicold
Critical

Check UL1 Circuit

Failure in the unloader 1 (UL1) circuit.

Possible causes

  • Defective unloader solenoid
  • Cut wire in the control line
  • Solenoid valve mechanically stuck

Recommended actions

  • Perform solenoid test from the technician menu
  • Measure continuity of the UL1 circuit
  • Verify valve activation

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