MrCool · Mini-Split Moderate
E5 — Indoor Coil Sensor (T2) Fault
E5 means the indoor evaporator coil temperature sensor (T2 thermistor) is open or shorted, so the unit can't read coil temperature for freeze protection and mode control.
- Keep using it?
- Yes, with caution
- DIY difficulty
- Hard
- Typical cost
- $15-30
- Verified against
- support.mrcool.com ↗
The fix
MrCool indoor unit coil temperature sensor/thermistor
Evaporator coil temperature sensor (T2 thermistor) open or shorted
Diagnose first: Same sensor family and DIY-replaceable as E4 — check the wiring connector first.
Find this part on Amazon →As an Amazon Associate we earn from qualifying purchases.
How to fix it
- Power-cycle at the breaker: off for five minutes, back on.
- If E5 returns, call an HVAC technician. The coil sensor is clipped deep on the evaporator inside the indoor unit — reaching and testing it is a technician job.
- What the technician will do: test the T2 sensor's resistance and replace it if failed. It is a small, inexpensive part; most of the visit is access and verification. Avoid running long cooling cycles until it is fixed — this sensor is what prevents the coil from icing over.
Why it happens
Typical signs: Unit stops or won't heat/cool properly · E5 on the display
- Failed T2 coil thermistor The evaporator coil sensor has failed.
- Loose sensor connector The T2 plug on the indoor board is loose.
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.