F2 — Outdoor Coil Sensor (T3) Fault
F2 means the outdoor condenser coil temperature sensor (T3 thermistor) is reading open or shorted.
- Keep using it?
- Yes, with caution
- DIY difficulty
- Hard
- Typical cost
- $15-30
- Verified against
- support.mrcool.com ↗
The fix
MrCool outdoor unit condenser coil temperature sensor
Condenser coil temperature sensor (T3 thermistor) open or shorted
Diagnose first: Same DIY-replaceable sensor family as F1 — inspect the connector before ordering a replacement.
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How to fix it
- Power-cycle at the breaker: off for five minutes, back on.
- If F2 returns, call an HVAC technician. The coil sensor is attached to the condenser coil inside the outdoor cabinet — panel-open, technician territory.
- What the technician will do: test the T3 sensor against specification and replace it if failed. It is a small part; the visit is mostly access and confirming nothing else drove the reading out of range.
Why it happens
Typical signs: Reduced performance or shutdown · F2 on the display
- Failed T3 coil sensor The condenser coil thermistor has failed.
- Loose connector The T3 plug on the outdoor board is loose.
More MrCool mini-split codes
Frequently asked questions
What does the F2 code mean on a MrCool mini-split?
F2 means the outdoor condenser coil temperature sensor (T3 thermistor) is reading open or shorted.
What causes the F2 code on a MrCool mini-split?
Failed T3 coil sensor: The condenser coil thermistor has failed. Loose connector: The T3 plug on the outdoor board is loose.
Is it safe to keep using a MrCool mini-split with a F2 error?
Yes, with caution. This is rated a moderate-severity fault.
How do I fix F2 on a MrCool mini-split?
Power-cycle at the breaker: off for five minutes, back on. If F2 returns, call an HVAC technician. The coil sensor is attached to the condenser coil inside the outdoor cabinet — panel-open, technician territory. What the technician will do: test the T3 sensor against specification and replace it if failed. It is a small part; the visit is mostly access and confirming nothing else drove the reading out of range.
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.