Carrier F5

What does Carrier F5 mean?

The control reports the discharge temperature sensor as open or shorted. Carrier's repair method is to measure the resistance value in the sensor, since the compressor's discharge temperature must be monitored to protect it. With no valid reading, the system flags F5 and stops running normally.

Symptoms

• F5 shown on the indoor unit display
• Discharge temperature monitoring lost
• System will not run normally
• Fault isolated to the discharge sensor

Common causes

• Open or shorted discharge temperature sensor
• Sensor resistance outside specification
• Damaged sensor wiring on the discharge line
• Loose connection at the outdoor board

Diagnostic steps

1. 01

   Confirm the F5 code

   Verify F5 on the indoor unit display first.

2. 02

   Measure the sensor resistance

   Follow the manual and measure the resistance value in the discharge temperature sensor.

3. 03

   Test for open or short

   Compare the reading to the manufacturer's chart to confirm an open or shorted condition.

4. 04

   Replace and verify

   Replace a faulty sensor and confirm the F5 code clears after restart.

When to call a professional

The discharge sensor mounts on the compressor discharge line inside the outdoor unit, near high-temperature and high-pressure components. If you are not equipped to safely test for open or short conditions and replace the correct sensor, have a licensed HVAC technician handle it. Compressor-protection sensors should be serviced by a qualified professional to avoid masking a real compressor problem.