Daikin VRV IV RXTQ-TA / RXTQ-TB error code A1
Indoor unit control board abnormality
Which models this applies to. Indoor unit
Quick answer
On Daikin VRV IV RXTQ-TA / RXTQ-TB, A1 is a fault. It means indoor unit control board abnormality. A first thing to check: A failed indoor unit control board.
- Applies to
- Daikin VRV IV RXTQ-TA / RXTQ-TB
- Daikin VRV IV RXTQ heat pump codes · Heat Pump
- Type of code
- Fault
- Urgency: Needs attention soon
- First safe check
- Confirm the error is reproducible after a power cycle, because a single occurrence on a large system is worth monitoring rather than replacing a board over.
What A1 means on this model
The indoor unit control board has detected a fault in itself or in an output it drives, and the unit has stopped. Check the link to the fan board before replacing this board, because C1 and C6 point at that connection specifically.
Symptoms you will notice
- Indoor unit shows A1 and stops
- The unit will not respond to the remote controller
- The operation lamp blinks with no other symptom
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 indoor unit control board
- A shorted output on the board
- A wiring or connector fault the board is reporting
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.
- Confirm the error is reproducible after a power cycle, because a single occurrence on a large system is worth monitoring rather than replacing a board over.
- Check the connectors between the indoor unit PCB and the fan PCB, since those are the most common physical fault on this class of board.
Do not do these
- ×Do not replace the indoor unit PCB before ruling out the fan board link, because C1 and C6 point at that connection and replacing the wrong board is an expensive mistake.
- ×Do not work on connectors with the power switch on. The manual states plainly that parts may be damaged otherwise.
When to call a technician
Book a technician, do not keep resetting it
This fault will not clear on its own. Every power cycle gives the control one more failed attempt, and repeated attempts are what turn a cheap part replacement into a seized or contaminated system.
- 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
Indoor unit control PCB $200 to $450. Fan PCB $150 to $350.
Labor
One to two hours to diagnose 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.