Carrier AC Error Code E5 — Outdoor Temperature Sensor Fault

What Does This Error Mean?

E5 on a Carrier AC means the outdoor ambient temperature thermistor has a fault. This sensor measures the outside air temperature so the inverter can adjust its operation for efficiency and protection. When the sensor fails or reads an impossible value, Carrier shuts down the system.

Affected Models

Carrier Ester Plus
Carrier Superia Plus
Carrier Durafresh Neo
Carrier Inverter Split AC (all models)
Carrier Esko Plus

Common Causes

Outdoor ambient thermistor has failed — resistance value out of specification
Thermistor connector loose or corroded at the outdoor PCB
Thermistor wiring damaged by weather or rodents
Thermistor probe dislodged from its mounting position
Outdoor PCB fault causing incorrect sensor reading

How to Fix It

Turn off the AC and switch off the circuit breaker.

Wait 5 minutes, restore power, and attempt one restart.
If E5 clears after a power cycle, monitor the AC for the next hour.

A transient sensor fault from a brief moisture event may not return. If E5 comes back after the system has been running a while, the sensor is genuinely faulty.
If E5 persists, call a Carrier authorised service agent.

Carrier has a service network across India and internationally. Contact Carrier customer support or the dealer who installed your unit.

When to Call a Professional

E5 requires a Carrier authorised technician. The outdoor ambient thermistor is inside the outdoor unit. A technician will measure the thermistor resistance and replace it if readings are outside the Carrier specification.

Frequently Asked Questions

Is E5 an expensive repair on a Carrier AC?

The thermistor part is inexpensive — typically Rs 200–600 in India or $10–25 internationally. The majority of the cost is the technician's visit. For units under warranty, thermistor replacement is covered.

Can extreme cold trigger a false E5 on a Carrier AC?

If outdoor temperatures drop very close to or below the thermistor's measurement range, a marginal sensor may produce an out-of-range reading. This is rare but can happen in unusually cold conditions. A robust thermistor will recover when temperatures normalise.