MrCool · Mini-Split Serious
F3 — Compressor Discharge Sensor (TP) Fault
F3 means the compressor discharge temperature sensor (TP thermistor) is open, shorted, or reading a dangerously high temperature. The unit protects the compressor by shutting down.
- Keep using it?
- Limited use only
- DIY difficulty
- Hard
- Verified against
- support.mrcool.com ↗
How to fix it
- Power-cycle once at the breaker: off for five minutes, back on. Do not keep repeating this — F3 exists to protect the compressor from running too hot.
- Make sure the outdoor unit can breathe: clear debris, vegetation, and anything blocking airflow around it. Poor heat rejection pushes discharge temperature up.
- If F3 returns, call an HVAC technician promptly and stop running the system — a genuinely hot compressor is being damaged every time it runs.
- What the technician will do: test the TP sensor first (a failed sensor is the cheap outcome), then check refrigerant charge and system pressures if the high reading is real. Low charge is a classic cause of high discharge temperature, and diagnosing it is gauge work.
Why it happens
Typical signs: Outdoor unit stops · Poor heating/cooling · F3 on the display
- Failed discharge thermistor The TP sensor on the compressor has failed.
- Low refrigerant charge A low charge makes the compressor run hot, raising discharge temperature.
Parts you may need
If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.
- Mini-Split Outdoor Sensor Kit Common replacementAmazon →
More MrCool mini-split codes
Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: support.mrcool.com.