Rheem mini split error code F3

Common causes

• The outdoor ambient temperature thermistor has failed (they do drift and fail with age and heat cycling).
• Its plug has worked loose from the control board, or a pin has corroded.
• The sensor lead is chafed, pinched or chewed, giving an intermittent open or short.
• The control board's sensor input has failed (rare compared with the sensor itself).

How to fix it yourself

Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician.

1. Reset the system: switch the breaker (or the outdoor disconnect) off, wait a full five minutes so the boards fully discharge, then switch it back on and restart from the remote.
2. If the code comes straight back after a reset, the fault is real and not a glitch.
3. With power off, locate the outdoor ambient temperature sensor clipped near the coil guard, sensing outside air. Follow its lead back to the board and reseat the plug firmly.
4. Inspect the lead for damage along its whole length, especially where it passes through the chassis.
5. If you have a multimeter, unplug the sensor and measure its resistance. A reading near zero ohms (short) or infinite (open) confirms a bad sensor. Most mini split thermistors read roughly 5 to 20 kΩ at room temperature, so a value in that range with a steady drift as you warm it in your hand means the sensor is fine and the board is the suspect.
6. Replacement thermistors are inexpensive and plug in. Match the part number from the parts list for your model.

Switch off power at the breaker before opening either unit. Capacitors in the outdoor unit hold a charge for several minutes after power is cut.

When to call a technician

Sensor swaps are a doable DIY job on most units. Call a technician if the sensor tests good and the code persists, because that points at the control board.

Which Rheem units show F3

This page applies to Rheem Classic and Classic Plus wall-mount (RIWH / ROWH), Endeavor Line multi-zone and Floating Air series (2023 and later) units on the Floating Air series (Friedrich-built, Gree platform). Rheem's own documentation lists F3 as "Outdoor ambient temperature sensor fault (open or short circuit)", the same definition used across the Gree platform it is built on. If your unit shows a code with a different shape (for example a four-character code, or a plain number), it is from a different table; use the lookup with your exact code.

Where Rheem shows this code

Floating Air series (Friedrich-built, Gree platform): The code shows on the indoor unit's display in place of the temperature. If the display is off, press the Light button on the remote. Some models also count out the code as indicator blinks. E codes are system protections and faults, F codes are mostly sensor faults, H codes are outdoor and compressor protections, U codes are motor and valve faults, and P codes are power-supply faults.

Other Rheem codes

Same part of the system as F3:

All Rheem error codes

F3 on other brands

The same characters do not always mean the same thing. Check the brand on your unit.

• Pioneer F3 Compressor discharge temperature sensor (TP) open or short circuit / Zone C indoor coil outlet sensor (T2B) fault, shown on the outdoor display
• Blueridge F3 Outdoor ambient temperature sensor fault (open or short circuit) / Compressor discharge temperature sensor (TP) open or short circuit
• Gree F3 Outdoor ambient temperature sensor fault (open or short circuit)
• Zone Air F3 Outdoor coil temperature sensor fault protection
• Daikin F3 Discharge pipe temperature too high
• Carrier F3 Compressor discharge temperature sensor (TP) open or short circuit
• Heil F3 Compressor discharge temperature sensor (TP) open or short circuit / Outdoor ambient temperature sensor fault (open or short circuit)
• ACiQ F3 Compressor discharge temperature sensor (TP) open or short circuit / Outdoor coil temperature sensor fault protection