J6Daikin · VRV IV RXTQ-TA / RXTQ-TB · Heat Pump

Daikin VRV IV RXTQ-TA / RXTQ-TB error code J6

Outdoor heat exchanger deicer thermistor abnormality, R4T

Book a technician

Also written as R4T, defrost sensor, icing, J6

Which models this applies to. Outdoor unit

What is specific to the VRV IV RXTQ-TA / RXTQ-TB platform

The RXTQ outdoor unit serves VRV indoor units over a shared communication bus, and the factory splits the code list by which unit reports it. A and C codes come from indoor units, E, F, H, J, L and P from the outdoor unit, and U and M are system or centralized controller faults. This is a commercial and light commercial multi split platform, not a residential one indoor mini split unit.

Your control board prints the code as text, for example F01 or EE3, so you read it off the display rather than counting blinks. The printed number is the fault itself, not a position in a table.

Quick answer

On Daikin VRV IV RXTQ-TA / RXTQ-TB, J6 is a fault. It means outdoor heat exchanger deicer thermistor abnormality, r4t. A first thing to check: A failed R4T thermistor.

Applies to: Daikin VRV IV RXTQ-TA / RXTQ-TB; Daikin VRV IV RXTQ heat pump codes · Heat Pump
Type of code: Fault; Urgency: Book a technician
First safe check: Check for ice or snow on the outdoor coil, because a sensor buried in ice will read falsely and can be physically damaged by it.

Checked 2026-09-26

What J6 means on this model

The R4T thermistor that monitors the coil during a defrost has reported a fault. The defrost cycle is temperature controlled from this reading, so the control stops rather than guessing and icing the coil. Check for ice or snow on the coil as well, because a buried sensor can be physically damaged.

Symptoms you will notice

Outdoor unit shows J6 and the system stops
The system will not complete a heating cycle
The system will not start a defrost
Ice builds up on the outdoor coil in a fault that is left alone

Common causes

The code tells you what the control detected, not which part failed. These are the causes we see most often, roughly in order of likelihood:

A failed R4T thermistor
A loose or broken wire at the thermistor
A disturbed connector
A sensor that has moved away from the coil
Ice or snow that has damaged or buried the sensor

What you can safely check

These are homeowner-level checks. None of them need you to open a live electrical compartment or work on gas.

Check for ice or snow on the outdoor coil, because a sensor buried in ice will read falsely and can be physically damaged by it.
Check that R4T is still in position on the coil and that the wire is not cut by the defrost operation.
Check the connector at the sensor.

Do not do these

×Do not chip ice off the outdoor coil with a sharp tool. It can cut the coil and the R4T wire, which turns a reading fault into a refrigerant leak.
×Do not leave J6 in place through a heating season. A control that cannot see the coil during defrost is a control that will ice the coil.

When to call a technician

Worth scheduling, and worth your own checks first

You can usually keep living with this for a short while, but it will not fix itself. Do the safe checks below first, because a tripped switch or a blocked airflow is a five-minute fix that would otherwise cost you a service call.

The refrigerant circuit is sealed and legally requires licensed handling. Opening it without certification releases refrigerant and can put the whole system in violation of regulation, so a low-pressure or high-pressure fault on this equipment is a call-out, not a weekend job.
If the appliance has stopped mid-cycle, is making a noise you have not heard before, or smells burnt, stop reading here and call. Those are symptoms of something the fault code does not describe well enough.

A technician job. Noticing ice on the outdoor coil is a reasonable homeowner observation.

What it costs to fix

Parts

Deicer thermistor $30 to $90.

Labor

One to two hours to test and replace.

DIY or technician