Friedrich mini split error code F4

Common causes

• The outdoor condenser coil (middle) 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 condenser coil (middle) temperature sensor in a well on the condenser coil behind the service panel. 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 Friedrich units show F4

This page applies to Friedrich Floating Air Select (FSHW / FSHSW, 2015-2019), Floating Air Pro and Floating Air Premier units. Friedrich's own documentation lists F4 as "Outdoor condenser coil (middle) 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 Friedrich shows this code

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 Friedrich codes

Same part of the system as F4:

All Friedrich error codes

F4 on other brands

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

• Pioneer F4 Outdoor unit EEPROM parameter error / Zone D indoor coil outlet sensor (T2B) fault, shown on the outdoor display
• Blueridge F4 Outdoor condenser coil (middle) temperature sensor fault (open or short circuit) / Outdoor unit EEPROM parameter error
• Gree F4 Outdoor condenser coil (middle) temperature sensor fault (open or short circuit)
• Zone Air F4 Cooling system gas flow abnormality protection
• Carrier F4 Outdoor unit EEPROM parameter error
• Heil F4 Outdoor unit EEPROM parameter error / Outdoor condenser coil (middle) temperature sensor fault (open or short circuit)
• ACiQ F4 Outdoor unit EEPROM parameter error / Cooling system gas flow abnormality protection