Daikin VRV IV RXTQ-TA / RXTQ-TB error code CA
Discharge air thermistor abnormality
Which models this applies to. Indoor unit
Quick answer
On Daikin VRV IV RXTQ-TA / RXTQ-TB, CA is a fault. It means discharge air thermistor abnormality. A first thing to check: A failed discharge air 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 that the thermistor is still mounted where it reads leaving air, and that the clip has not been moved during a service.
What CA means on this model
The sensor reading the air leaving the indoor coil is not reporting a usable value. The control uses it to judge supply temperature, so it stops rather than guess.
Symptoms you will notice
- Indoor unit shows CA and stops
- The unit will not heat or cool
- The unit short cycles once it starts
- The sensor or its connector was disturbed during a fan or coil service
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 discharge air thermistor
- A loose or broken wire at the thermistor
- A disturbed connector
- A clip that has come loose so the sensor no longer reads the leaving air
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 that the thermistor is still mounted where it reads leaving air, and that the clip has not been moved during a service.
- Check the connector and the wire at the sensor.
- Compare the resistance against the air temperature using the chart in the manual.
Do not do these
- ×Do not relocate the discharge air sensor to make a code clear. The control uses it as a supply air measurement and moving it invalidates the reading.
- ×Do not work on the connector with the power switch on.
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.
What it costs to fix
Parts
Thermistor $30 to $90.
Labor
One to two hours to test and replace.
DIY or technician
A technician job.
Typical US part and labor ranges, 2026. They vary by region, model and contractor, so treat them as a planning figure, not a quote.
Scope of this code
- Code table
- Daikin VRV IV RXTQ heat pump codes
- Models in scope
- Daikin VRV IV RXTQ-TA / RXTQ-TB
- Checked
- Confirm on your own unit
- Find the model number on the data plate, then check this code in the service manual for that model. Manufacturers revise code tables between model years, and a revised board can renumber a fault.